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In this study, the comprehensive study of the performance investigation of Solid Desiccant Based Dehumidification (SDBD) system which involves the desiccant selection and desiccant coating with metallic heat exchanger was conducted at the mild humid conditions which represent the humid air conditions in summer, South Korea. The water uptake capacity of three different solid desiccants was investigated to find the proper solid desiccant in the SDBD system under the given operating conditions. Among the three different solid desiccants, the aluminum fumarate based metal organic frameworks (MOFs) was selected as the best solid desiccant for SDBD system and it has the maximum water uptake capacity around 0.398 g·g−1 for given operating conditions. The aluminum fumarate based metal organic frame works (MOFs) was coated on the metallic surface of heat exchanger by current developed coating method and the desiccant and binder solution is consistent of 10% of binder and solvent mixture and 90% of aluminum fumarate based MOFs. As a result, the increase of coating thickness from 0.05 mm to 0.2 mm and operating time from 150 s to 300 s can achieve the 113% and 131% of dehumidification performance enhancement in average, respectively. Remarkably, over 160% improvement of dehumidification performance in average can be achieved by the decrease of space velocity from 13 s−1 to 5.2 s−1.

Most previous studies on adsorption chillers were conducted using the same adsorption and desorption times. Instead, this study analyzed various adsorption/desorption time allocations, and systematically examined the effect of cycle time allocation on system performance. The results provide physical insights for 3-bed adsorption chillers. The effect of hot water temperature and cycle time on the optimum adsorption/desorption time ratio was also examined. Setting the proper adsorption and desorption times was much more important for smaller cycle times. The highest degradation in COP (coefficient of performance) found was 36% at 300 s of cycle time, compared with the conventional 1:1 ratio. When the temperature of the heat source is low, the ratio of adsorption/desorption time was not significantly affected, however, for higher performance at high temperature, a longer adsorption time than desorption time was required.

An adsorption chiller is a highly promising cooling technology, but it has not been widespread because there are many uncertainties to solve the complex thermal and mass transfer phenomena. An adsorption chiller is composed of multi-modules and the tube inlet temperature decreases (or increases) during the adsorption process (or desorption process) from module to module in serially connected modules. It has been reported that the optimal fin height depends on the tube inlet temperature, thus using a different fin height for each module should potentially enhance the overall system performance of the adsorption chiller. Till now, there have been few studies which evaluated adsorption chiller performance from a system viewpoint. Most only considered a single fin space. Thus, no study has considered improving total system performance by using different conditions for different modules in series. We conducted a numerical study of 5 modules in series, using different fin heights. The coefficient of performance (COP) and specific cooling power (SCP) of modules with stepwise-linearly decreasing fin height were compared with those of modules with constant fin height. An 8.5% increase in COP and a 9.56% increase in SCP were observed. This enhancement will be much larger if more than five modules are connected to match the cooling capacity. The decrease (or increase) in tube inlet temperature accumulated in the series of modules. The last module, the 5th showed the most significant enhancement in COP and SCP, of 27.9% and 38.4%, respectively.

To overcome the problem of peak electricity demand caused by the use of air-conditioning in the summer, researchers have been focusing their interest on adsorption chillers, which are an environmentally friendly technology in that they use waste heat as their power source and water as a refrigerant. In the present study, to improve the performance of an adsorption chiller, FAPO4-5 adsorbents were synthesized using two hydrothermal synthetic methods, and then characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption/desorption isotherms and water adsorption isotherms. Coatings of the adsorbent were applied to an aluminum substrate. Six different coating solutions were used, with a 5.0 wt%, 10.0 wt%, and 15.0 wt% content of epoxy-based and silicone-based binders, respectively. The surface features of adsorbent coating were observed with scanning electron microscopy (SEM). To determine the variation in the water adsorption properties of the adsorbents according to the binder type, each adsorbent was subjected to water adsorption isotherm analysis at 25 °C. The coating thickness was calculated by three dimension coordinate measuring machine. Cross-cut tests (performed according to ISO 2409:2013) were carried out to assess the strength of the adhesion of the coating to the aluminum substrate.

In this research, automatic fouling cleaning systems that clean and prevent the deposit of fouling by regularly circulating sponge or ceramic balls are proposed. Characteristics of the finned and twisted inner tubes of the double pipe heat exchanger for the heat pump unit are also compared. Lastly, the 50RT-scale field test of the automatic fouling cleaning system integrated with the heat pump system was conducted by targeting temperature control of fish farms. The finned inner tube types presented a higher heat transfer rate than that of the twisted inner tube types. For the finned tube types, the refrigerant supply from the tangential direction was more advantageous due to the uniform distribution of refrigerant into 16 channels. The twisted tubes showed a higher water pressure drop than the finned inner tubes. An obvious increase in the fouling factor according to the operating hours was observed, however, it could be successfully decreased by operating the fouling cleaning system for 24 h. The overall heat transfer coefficient could be recovered from 5.87 kW/K to 24.05 kW/K, which is about 92% of the initial value. In short, the automatic fouling cleaning system can successfully prevent performance degradation of heat pump system due to fouling.

In this study, the performance evaluation of an adsorption chiller (AD) system with three different adsorbents—silica-gel, aluminum fumarate, and FAM-Z01—was conducted to investigate the effects of adsorption isotherms and physical properties on the system’s performance. In addition, the performance evaluation of the AD system for a low inlet hot-water temperature of 60 °C was performed to estimate the performance of the system when operated by low quality waste heat or sustainable energy sources. For the simulation work, a two-bed type AD system is considered, and silica-gel, metal organic frameworks (MOFs), and ferro-aluminophosphate (FAPO, FAM-Z01) were employed as adsorbents. The simulation results were well matched with the laboratory-scale experimental results and the maximum coefficient of performance (COP) difference was 7%. The cooling capacity and COP of the AD system were investigated at different operating conditions to discuss the influences of the adsorbents on the system performance. Through this study, the excellence of the adsorbent, which has an S-shaped isotherm graph, was presented. In addition, the influences of the physical properties of the adsorbent were also discussed with reference to the system performance. Among the three different adsorbents employed in the AD system, the FAM-Z01 shows the best performance at inlet hot water temperature of 60 °C, which can be obtained from waste heat or sustainable energy, where the cooling capacity and COP were 5.13 kW and 0.47, respectively.

Absorption heat transformer (AHT) has played a role in producing available heat from the low temperature of waste heat sources. This study proposes two operating modes regarding the way to supply heat source to the AHT system, and aims to investigate the operating characteristics of the steam generating AHT system concerning heating source temperature. First, this study describes the thermodynamic cycle of the single stage AHT operating with water-lithium bromide pair, and two operating modes are illuminated: a forward flow mode for heat source input to the evaporator and then to the generator, and a reverse flow mode for heat source input to the generator and then to the evaporator. Second, the first law of theoretical simulation characterizes the effects of the different operating modes on the heat transfer rates of each AHT component, the coefficient of performance (COP), and the steam generation rate. The experimental studies validate the theoretical simulation models; consequently, the results obtained herein lay a foundation of further investigation for the thermodynamic characteristics of the steam generating AHT system to maximize the operating performance.

In this study, we synthesized cross-linked poly methyl methacrylate beads and cross-linked fluorinated poly methacryalte copolymer (F-cPMMA) beads by the dispersion polymerization method with methyl methacrylate monomer, ethylene glycol dimethacrylate, and 2,2,2-trifuloroethyl methacrylate. The size of cross-linked PMMA and F-cPMMA beads was about 100 nm. Then we developed a new geometrical high-hydrophobic film by embedding the F-cPMMA nanobeads on polyurethane (PU) film. The PU film containing fluorinated poly methacryalte copolymer beads showed a greater hydrophobic property than the non-fluorinated one in the range of 1–10 wt.%. For the purpose of industrial application of the PU films, we applied 0.1–1 wt.% of beads on the fabric by the laminating method. The PU film containing 1 wt.% of fluorinated poly methacryalte copolymer beads, which was laminated onto nylon fabric, showed the best performance of hydrophobic property (water contact angle, 79°) and moisture vapor transmission rate (8797 g·m–2·24 h).

The applications of electronic expansion valves in high temperature heat pump have increased rapidly. However, correlations for predicting R245fa mass flow rate through electronic expansion valves in high temperature heat pump are very limited in open literatures. In this study, mass flow rate characteristics of R245fa refrigerant flowing through electronic expansion valves with different operational conditions are studied experimentally, and empirical correlations are proposed based on the experimental data. The results reveal that the mass flow rate increases with increasing opening degree, condensation temperature, subcooling, and orifice diameter. Based on a modified single phase orifice equation, two empirical correlations are proposed by using the power-law correlation and the polynomial fit correlation, and over 92% of the predicted data deviate from the experimental data within ±15%.

In the authors’ previous work, an embossed plate heat exchanger was proposed to the adsorption bed and results showed that the plate heat exchanger adsorption chiller had a lower Coefficient of performance (COP) but higher Specific cooling power (SCP) than those of a fin-tube type adsorption chiller, which shows high potential to resolve one of the most serious disadvantages of the adsorption cooling system, i.e., system size. However, only one section of the repeating embossed pitch plate was used and a uniform inlet flow condition was applied, which might have caused a distortion in estimated performance. We have reassessed the embossed plate heat exchanger adsorption bed by including the end effect to examine the real benefit of the proposed heat exchanger. The result showed that SCP was not significantly changed, while a 66.4 % increase in COP was observed. The proposed embossed plate heat exchanger adsorption bed is expected to provide advantages in both COP and SCP compared to a fin-tube type adsorption bed.

The absorber is one of the most important components in the LiBr-water absorption heat transformer (AHT) because it has the largest heat transfer area, and its performance significantly influences the overall system efficiency. Nevertheless, studies on absorbers used at the high-pressure level have not progressed. In this study, the horizontal tube falling film absorbers were constructed by introducing three types of heat transfer tubes (copper bare, copper-nickel bare, copper-nickel floral). The combined effects of the tube structure and material on the heat transfer performance of the absorber were experimentally investigated under the operating conditions of the single-stage AHTs. The experimental results showed that the film Reynolds number of 50 was optimal for the absorbers used in this study. At that point, the overall heat transfer coefficients of the copper bare tube, the copper-nickel bare tube, and the copper-nickel floral tube were 1,484, 1,448, and 1,299 W/m2 K, respectively. In addition, the heat transfer performance of the bare-type tubes was superior to that of the floral tube, except the under the low film Reynolds number. The empirical correlations of the Nusselt number for three types of heat transfer tubes were derived based on the experimental results and were predicted the data within the standard errors of 3.79–5.57 %.

In studies addressing performance degradations owing to frost formation on heat exchangers, the frost thickness is considered an important parameter. The most commonly used method for measuring frost thickness comprises capturing and analyzing an image. However, relatively few studies have investigated the most reasonable method for deriving frost thickness by analyzing an image. In current measurement techniques, it is difficult to quantitatively determine which methods have less error relative to the true value in a complex shape. Therefore, this study attempted to recommend a more reasonable method, based on analysis of various aspects. First, the fundamental concept of image processing was described in detail. Then, the effects of thresholding algorithms, threshold application algorithms, and the determination of the number of segments on the frost thickness were investigated. Based on the results, an appropriate image processing method for measuring frost thickness was recommended. The frost thickness obtained by this method was well-measured, with an uncertainty of approximately 0.18 mm.

In this paper, the mass flow rate characteristics of R245fa refrigerant flowing through electronic expansion valves (EEV) under varying operating conditions are studied experimentally. It is found that the mass flow rate increases with increasing EEV opening, condensing temperature, subcooling temperature, and orifice diameter. Based on the measured experimental data, two empirical correlations for mass flow rate prediction of R245fa through EEVs are proposed using the power-law correlation and the polynomial fit correlation. Predicted data of the polynomial fit method showed more consistency with the experimental results compared to that of power-law correlation, and 96.6% of the predicted mass flow rates deviate from the experimental data within ±10%.

In this paper, heat transfer characteristics of fin-tube heat exchanger and primary surface heat exchanger (PSHE) used in waste heat recovery were investigated experimentally. The flow in the fin-tube heat exchanger is cross flow and in PSHE counter flow. The variations of friction factor and Colburn j factor with air mass flow rate, and Nu number with Re number are presented. Various comparison methods are used to evaluate heat transfer performance, and the results show that the heat transfer rate of the PSHE is on average 17.3% larger than that of fin-tube heat exchanger when air mass flow rate is ranging from 1.24 to 3.45 kg/min. However, the PSHE causes higher pressure drop, and the fin-tube heat exchanger has a wider application range which leads to a 31.7% higher value of maximum heat transfer rate compared to that of the PSHE. Besides, under the same fan power per unit frontal surface, a higher heat transfer rate value is given in the fin-tube heat exchanger.

A parametric study on a heat-pipe type adsorption chiller with SWS-1L (mesoporous silica gel impregnated with CaCl2) and water pair was conducted using a numerical method in this research. A heat pipe that is in direct contact with the adsorbent is applied to the adsorption chiller to improve the heat transfer capacity of the adsorption bed. A feasibility study was performed on the heat-pipe type adsorption bed with a single layer. The Coefficient of performance (COP) and the Specific cooling power (SCP) were 0.231 and 844.8 W/kg, respectively. These values are lower than the system performance values of the existing fin-tube type adsorption bed. However, when the number of bed layers was increased to seven, the COP and SCP of the heat-pipe type adsorption bed were 0.520 and 752.4 W/kg, respectively. These values are 5.25 % and 39.8 % higher than the COP and SCP, respectively, of the fin-tube type adsorption bed. These findings indicate that the heat-pipe type adsorption bed can potentially address the disadvantage caused by the system size of the adsorption chiller. A parametric study was also conducted for six design parameters, namely, number of layers, heat pipe pitch, heat pipe radius, fin width, fin spacing, and hot water temperature.

New composite materials were prepared by impregnating CaCl 2 into FAPO 4 -5 to enhance the water adsorption capacity of the FAPO 4 -5 and limit the deliquescence of CaCl 2 . The structure of the FAPO 4 -5 was not changed after impregnation, as confirmed by the corresponding X-ray diffraction (XRD) patterns. The composite materials exhibited enhanced water adsorption capacity (up to 08 g/g-sorbent at 50.0 wt% loading) within the working relative pressure range of water vapor of adsorption heat pump (AHP) systems (0.1–0.3 of water vapor relative pressure). The composite material with CaCl 2 loading up to 15.9 wt% can also minimizes deliquescence of the salt which is not preferable in AHP applications. Despite partial pore filling of CaCl 2 in the matrix, the adsorption capacities of the composites were comparable to the sum of the adsorption capacities of CaCl 2 and FAPO 4 -5 without significantly affecting that of the pristine FAPO 4 -5.

A numerical analysis was conducted to examine the effect of a coating technique on adsorption cooling system (ACS) performance compared to a fully-filled grain configuration. The main interest was the effect of coating thickness, binder and cycle time for adsorption cooling applications. Validation of the numerical model was confirmed by comparison with experiment. The coating configuration resulted in a larger interfacial area to open space and also a shorter length of vapor flow path compared to the fully-filled configuration, which enhanced the vapor flow and resulted in higher performance. The optimal coating thickness was found to be 0.2–0.5 mm. A short cycle time was enough for the coating configuration, which improved system performance. For example, at coating thickness t = 0.2 mm, a 34.17% enhancement in specific cooling power (SCP) was achieved with a shorter cycle time of 480 s rather than 840 s, with the penalty of 9.87% decrease in coefficient of performance (COP). The coating technique with reduced cycle time is a good design approach for adsorption cooling systems. The binder had a negative effect on system performance, but the coating technique had clear advantages compared to the fully-filled configuration, and there was no other way of binding the adsorbent particles together. Thus, it is recommended that the binder content be kept as small as it can be.

In this study, we prepared an adsorbent layer for adsorption heat pump by using ferroaluminophosphate (FAPO) particles and inorganic silica binder and characterized the physical properties thereof. We tried two ideas in preparing the adsorbent layer: dual precursor for binder and surface modification of the FAPO particles. The inorganic silica binder was prepared through a sol–gel process by using tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) as the dual precursor. The surface modification by TEOS molecules on the FAPO particles was done to promote the reactivity between particles and binder. The surface modification to form monolayer of silane was carefully done in a hydrophobic solvent, cyclohexane, preventing the supply of water molecules into the solution. As a result, both the use of dual precursor binder and the surface modification effectively improved the mechanical stability of the layer as shown by higher resistance to mechanical vibration. It was analyzed that the addition of MTES served to enhance the mechanical stability of the adsorbent layer by providing the flexible element, Si–C bonding, in the rigid inorganic matrix. To explain the microstructure analysis by SEM and TEM, and the zeta potential measurement, we proposed a surface reaction model comprising the formation of very thin layer of surface silanol on FAPO particles enhancing the reactivity between the particle and the binder. Both the dual precursor and the surface modification produced no noticeable detrimental effect on the key properties such as water vapor adsorption and thermal conductivity.

This paper investigates the characteristics of ferroaluminophosphate (FAM-Z01) compared to various types of conventional silica gels in the performance of an adsorption bed. FAM-Z01 has high potential to replace silica gel due to some key advantages, including a low heating temperature and high adsorption rate resulting from its S-shaped isotherm. We conducted a performance simulation on a fin-tube type adsorption bed with FAM-Z01/water and silica gel/water working pairs and compared the results in terms of coefficient of performance (COP) and specific cooling power (SCP). In the partial pressure range of typical operating condition for silica gels, there was no advantage with FAM-Z01. However, in the partial pressure range of 0.14

Ternary copper–carbon nanotube–silicon carbide (Cu–CNT–SiC) and copper–carbon nanotube–aluminum nitride (Cu–CNT–AlN) composite coatings, which were fabricated by mechanical alloying and cold gas dynamic spraying, were used as heating surfaces for boiling heat transfer enhancement. The surfaces of these composite coatings had randomly distributed micro- and nano-sized cavities, which served as active sites for bubble nucleation. Nucleate boiling heat transfer tests on the composite coatings were investigated in a pool of saturated R134a refrigerant at 4.8 ± 0.04 °C. Boiling inception on the Cu–CNT–SiC and Cu–CNT–AlN coatings started at heat flux values of about 10–20 kW/m2 and at wall superheats that were about 4 °C lower than that of the plain Cu plate. The Cu–CNT coating had maximum boiling heat transfer enhancement ratio Eh,max of 1.48 as compared to the plain Cu plate. With the addition of SiC and AlN particles into the composition of the Cu–5CNT composite, the enhancement was augmented further. The coating with 20 vol.% AlN exhibited the highest enhancement with an Eh,max of 2.83. This was followed by the coating with 10 vol.% SiC with an Eh,max equal to 2.52. Although the Cu–CNT–ceramic coatings had high Eh,max, the Eh decreased at high heat fluxes. The maximum enhancement by achieved by each of the composite coatings was observed at heat fluxes within 100–200 kW/m2.

The switching time is an important operating condition that must be correctly anticipated for an effective adsorption cooling system. Before the adsorption (or desorption) process begins, time is required to cool down (or heat up) the bed temperature so that the bed pressure reaches the evaporator pressure (or condenser pressure). During the switching time, the supplied heat is reduced and pressure overload conditions can be avoided. The switching time cannot be estimated early on, and an improper switching time degrades the system performance. Thus, this study provides guideline with which to determine the required time to open this valve, i.e., the switching time, and carefully examines the thermo-physical behavior in the adsorption bed during this period. A two-dimensional numerical method with the composite sorbent of SWS-1L and a water pair is applied to a fin-tube type adsorption chiller. Three cases of no switching time, the optimal switching time and a double the optimal switching time are examined. The results show that no consideration of the switching time overestimates the performance of the adsorption cooling system in terms of the Coefficient of performance (COP) and the Specific cooling power (SCP). On the other hand, if the switching time exceeds the optimal value, the performance of the adsorption cooling system is also reduced compared to that when using the optimal switching time. The dependency of the optimal switching times on various design parameters, such as the fin pitch, fin height and heating temperature, is also examined.

The present research conducted a parametric study on an embossed plate heat exchanger (plate HX) type adsorption chiller with SWS-1L and water pair, using a numerical method. The plate HX has a relatively high heat transfer capacity and compact size, and this study is a first attempt to apply the plate HX as a new type of adsorption chiller, as an improved alterative to the fin-tube type heat exchanger. A feasibility study was conducted on the base model and the result is comparable to the value for existing fin-tube type adsorption chillers. Furthermore, a parameter study was conducted for seven important design parameters, embossing diameter ratio, embossing height, embossing pitch, bed thickness, plate thickness, heating temperature and heat transfer fluid velocity. The results provided guidelines for the optimal designs of plate HX type adsorption chiller. The optimal values of COP and SCP were 0.5118 and 662.8 W kg −1 , respectively.

The objectives of this paper are to develop correlations between heat transfer and pressure drop for oval finned-tube heat exchanger with large diameters (larger than 20 mm) used in a textile machine dryer. Numerical tests using ANSYS CFX are performed for four different parameters; tube size, fin pitch, transverse tube pitch and longitudinal tube pitch. The numerical results showed that the Nusselt number and the friction factor are in a range of −16.2 ~ +3.1 to −7.7 ~ +3.9 %, respectively, compared with experimental results. It was found that the Nusselt number linearly increased with increasing Reynolds number, but the friction factor slightly decreased with increasing Reynolds number. It was also found that the variation of longitudinal tube pitch has little effect on the Nusselt number and friction factor than other parameters (below 2.0 and 2.5 %, respectively). This study proposed a new Nusselt number and friction factor correlation of the oval finned-tube heat exchanger with large diameters for textile machine dryer.

The formation and growth of frost in air source refrigeration systems cause degradation of the system’s performance. Super-hydrophobic technology can delay frost growth and it has received much attention. However, only a limited number of studies have investigated the effects of super-hydrophobic surfaces on frost growth. This study therefore investigated the effects of surface characteristics on frost retardation in heat exchangers with various fin pitches. Heat exchangers with bare, hydrophobic, and super-hydrophobic surfaces were tested, and their frost retardation capabilities were evaluated by comparing the time taken for the air flow passage to be blocked. Hydrophobic and super-hydrophobic surfaces delayed the time by an average of 14.4% and 42.0%, respectively, compared to bare surfaces. The effect of surface characteristics on the heat transfer rate and pressure drop of the heat exchanger was also evaluated. Super-hydrophobic surfaces reduced the decrease in the heat transfer rate and increased the pressure drop by 14.4% and 470%, respectively, compared to bare surfaces. For a system that involves repeated frosting and defrosting, it is estimated that the super-hydrophobic surface can increase the average heat transfer rate by approximately 4.8% more than a bare surface.

Ternary copper (Cu)–carbon nanotube (CNT)–aluminum nitride (AlN) composite coatings were consolidated by the cold gas dynamic spray (CGDS) deposition of mechanically alloyed (MA) powders. The MA powder and CGDS coating samples were characterized by weight and size measurements, optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The porosity and roughness of the coatings were examined by porosimetry and profilometry, respectively. Also, the wettability of the coatings in saturated liquid R134a refrigerant was investigated. The EDX analysis depicted the non-homogeneous dispersion of the AlN as well as the CNT. The XRD results revealed that the composite powders and coatings had undergone microstraining and grain size reduction due to deformation. Metallographic examination showed that the coating internal microstructures had lamellar and compacted features, which evidenced the severe deformation that resulted from the impact during particle deposition. Although the coatings had externally porous surfaces, they had dense and non-porous internal microstructures. Moreover, smaller pores were located inside the larger pores or craters on the surfaces. The addition of 10 vol.% and 20 vol.% AlN into the Cu–5CNT mixture produced ternary Cu–CNT–AlN composite coatings with fine pores that were directly open to the surfaces. Lastly, the coatings with AlN were more wettable in liquid R134a than the plain Cu plate and pure Cu and Cu–5CNT coatings.

Ternary copper (Cu)–carbon nanotube (CNT)–silicon carbide (SiC) composite powders were prepared by mechanical alloying (MA). These MA composite powders were spray deposited as coatings on Cu plate substrates by cold gas dynamic spraying (CGDS). Characterizations of the MA powders and CGDS coatings were conducted by size and weight measurements, optical microscopy, scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The coating surfaces were also examined by mercury porosimetry and stylus profilometry. The results showed that the addition of SiC in the Cu–5CNT powder mixture led to particle size reduction after MA. The deposition efficiency of the Cu–CNT–SiC composite powders as CGDS feedstock increased when the SiC content was increased from 10 vol% to 20 vol%. The dispersion of SiC in the composite powder particles and coatings was not homogeneous as revealed by the EDX elemental mappings. As examined by XRD, the SiC as well as the CNT and the Cu had undergone microstructural changes (e.g., microstraining, grain refinement, and partial amorphization) due to the deformation caused by MA and CGDS. The addition of SiC, combined with the strain hardening due to MA and CGDS, resulted in coatings with significantly higher hardness than the coatings without SiC. Using CGDS, the MA Cu–CNT–SiC composite powders produced coatings with microporous surfaces and dense internal microstructures as evidenced by the SEM, profilometry, and porosimetry results. Lastly, the surface pores of the Cu–CNT–SiC coatings were finer than those of the pure Cu and Cu–5CNT coatings.

The objective of this paper is to provide design data of fin-tube heat exchanger which have a large diameter ovaltube for dryer application. In this study, the heat transfer and pressure drop performance characteristics of the fin-tube heatexchanger were compared with Dittus-Boelter and a new correlation equation using Wilson plot method. The simulationresults based on section by section method were compared with experimental results. These results showed that a new correlationequation using Wilson plot method provided better prediction, about 3 to 12%, than the Dittus-Boelter equation, from theexperiment comparison. Also, the pressure drop of simulation results showed much more deviation with the experimentalresults.. Key words Fin-tube heat exchanger(핀-관 열교환기), Heat transfer coefficient(열전달계수), Oval tube(타원관), Prssure drop(압력강하)†Corresponding author, E-mail: kwonok@kitech.re.kr 기호설명 A ： 면적 [ ㎡ ] C ： 열용량 [W/k] D ： 직경 [m] D h ： 열교환기 수력직경 [m] F p ： 핀간격 [m] h ： 열전달계수 [W/ ㎡․ K] k

This paper presents a numerical analysis of the performance of a fin-tube type adsorption chiller associated with heat and mass transfer mechanisms. A two-dimensional axisymmetric transient model is developed and 10 parameters are used to investigate their effects on the performance of an adsorption chiller and to obtain the optimized conditions of a fin-tube type adsorption chiller. Ten parameters found in many other studies, such as fin pitch, fin thickness, fin height, diffusion coefficient, particle size, cycle time, cycle ratio, temperature of hot water, fluid velocity and porosity, are used in this study. Based on the design of experiment, an orthogonal array of 10 parameters with three levels, L 27 (3 13 ) is used for the analysis of variance (ANOVA) and through this method, each parameter's level of contribution is carefully examined. The result shows that fin thickness and the temperature of hot water are the dominant parameters for COP and SCP, respectively. The optimum conditions having the highest COP of 0.6782 and SCP of 217.68 W kg −1 are found through the result.

This study presents a numerical investigation of the heat and mass transfer kinetics of a fin-tube type adsorption bed using a twodimensional numerical model with silica-gel/water as the adsorbent and refrigerant pair. The performance is strongly affected by the heat and mass transfer in the adsorption bed, but the details of the mass transfer kinetics remain unclear. The validity of intra-particle models used to simulate mass transfer kinetics such as the equilibrium, LDF, and solid-diffusion models are examined, and the valid ranges of the diffusion ratio for each model are proposed. An intra-particle diffusion model should be carefully implemented; otherwise, seriously distorted results may be produced, i.e., over-estimation for the equilibrium model and under estimation for the LDF model.

In the present study, the effect of MWCNT/Fe coatings on steel substrate was investigated using R134a vapor. Specifically, CNT and Fe2O3 powder were used as components in mechanically alloyed powder composites, which were used to fabricate surface coatings. There were two types of coatings used in the tests. The first one was pure Fe coating and the second one was the MWCNT/Fe composite coating. The powders were coated on a plain carbon steel plate by electrostatic spraying. This was followed by sintering at 900 °C. Results showed that the condensation heat transfer can be enhanced by MWCNT/Fe composite coatings, while a pure Fe coating can diminish the enhancement in comparison to the plain carbon steel plate.

The objectives of this study are to measure the ball recovery rate of cleaning apparatus for plate heat exchanger. Ceramic ball is used for plate heat exchanger cleaning. The main components of cleaning apparatus are comprised of ball collector, ball trap, ejector, pump and plate heat exchanger. The ball recovery rate are obtained with change in recovery time and velocity of water. The results show that the ball recovery rate is slightly increased with increase in the recovery time and the velocity of water over 0.4 m/s in the straight flow. In the case of reverse flow, the ball recovery rate more increased than straight flow. The maximum ball recovery rate of the straight flow and reverse flow reach 83.97% and 86.61%, respectively, when the velocity and cleaning time are 0.5 m/s and 15min.

The present study investigated a two-stage compression heat pump system for district heating utilizing waste energy. An evaporator and condenser exhibit a large difference in temperature when hot water is produced for heating by a heat pump. With single-stage compression, this causes a dramatic drop in the compressor efficiency and lowers the system performance; so, in the present study, a two-stage compression heat pump system comprising an intercooler and flash tank was designed, and the performance characteristics under various operating conditions were tested. When the heat source temperature was raised from 10 °C to 30 °C, the COP (coefficient of performance) was improved by up to 22.6%. As the superheating at the low-stage compressor was increased from 2 °C to 11 °C, the refrigerant flow rate and heating capacity decreased by as much as 7.6% and 2.2%, respectively, but there was no major impact on the temperature of the hot water produced nor on the system performance. Controlling the frequency of the high-stage compressor to control the intermediate pressure resulted in the ability to improve performance by as much as 5.2% under identical heat source conditions.

The analysis of performance characteristics was carried out in the plate type evaporator with counter and parallel flow. To investigate performance of evaporator with water inlet temperature and refrigerant mass flow rate were changed. As a result, when the inlet temperature of water is 8 o C, capacity of parallel flow evaporator higher than counter flow is 0.35%. But as the inlet temperature of water rises from 8 o C to 16 o C, capacity of counter flow type evaporator higher than parallel flow type is 0.12%, 0.27%, 1.1%, 1.6%, respectively. The findings showed that counter flow type evaporator has a larger capacity than those that were parallel flow type evaporator. As the refrigerant mass flow rate rises, capacity and pressure drop increases in the counter and parallel flow type evaporator. Key Words ：Counter flow, Parallel flow, Evaporator, Plate heat exchanger, R410a *†권오경(교신저자) : 한국생산기술연구원E-mail : kwonok@kitech.re.kr, Tel : 041-589-8528 *배경진 : 한국생산기술연구원*차동안 : 한국생산기술연구원*†Oh-Kyung Kwon(corresponding author) : Energy System R&D Group, Korea Institute of Industrial Technology.E-mail : kwonok@kitech.re.kr, Tel : 041-589-8528 *Kyung-Jin Bae : Energy System R&D Group, Korea Instituteof Industrial Technology.*Dong-An Cha : Energy System R&D Group, Korea Institute of Industrial Technology.

The objective of this study is to investigate the performance of a two-stage com-pression heat pump system for district heating. The experimental setup of heat pump consists of compressor, condenser, evaporator, expansion device, intercooler, flash tank, oil separator and accumulator. The experimental evaluations on the two-stage compression cycle were carried out under various operating conditions which were heat source temperature, the degree of compressor inlet superheat, and intermediate pressure. The temperature ranges of unutilized energy as the heat source were used in the test conditions. As the heat source temperature increased from 10℃ to 30℃, the COP and heating capacity of the heat pump system increased by 22.6% and 45.8%, respectively. The performance of the two-stage heat pump system increased by 5.2% with the variation of the intermediate pressure in the same heat source temperature conditions.Keywords:District heating(지역난방), Intermediate pressure(중간압), Two-stage compression heat pump(2단 압축 히트펌프), Unutilized energy(미활용에너지)

Gold, silver, and platinum nanoparticles were immobilized on the surface of TiO2 in the sheath part of bi-component filaments. The processes involved include the spinning process used to prepare polyethylene terephthalate (PET)/PET-TiO2 bi-component filaments and the photocatalytic deposition process of gold, silver and platinum nanoparticles. The core part and the sheath part consist of virgin PET and 4 wt.% of TiO2 compounded PET, respectively. The sheath: core ratio of the filament was 50:50. For the photo-deposition of metal nanoparticles, adsorption of the metal ions on the surface of the fabrics was performed by immersing them in AgNO3, HAuCl4, and H2PtCl6 aqueous solutions, with simultaneous addition of methanol as a sacrificial agent. Photo-deposition was then carried out under UV light with an irradiation time of 60 seconds. The structural and antibacterial properties of the bi-component filaments were characterized. The nano-sized noble metal particles in a polka dot form were observed around the surface of the TiO2 particles in sheath region of bi-component filaments after photocatalytic deposition. Ag, Au, and Pt metal photo-deposited fabrics showed excellent antimicrobial effect against the two types of bacteria Staphylococcus aureus and Klebsiella pneumoniae under dark conditions.

Key Words: Control(제어), EEV(전자식팽창밸브), PCW(냉각수), PWM(펄스폭변조방식), SemiconductorChiller(반도체칠러), Step Moter Operated(스텝모터구동방식)초록: 본연구에서는전자식팽창밸브를적용한반도체공정용칠러에관한실험적연구를통해시스템특성을파악하였다. 또한온도변화에따른신속한대응을할수있도록온도상승및하강실험, 부하변화에따른온도영역별제어정밀도실험을함으로써각제어방식에따른운전특성을파악하였다. 온도상승시소비전력은8.9 kW로측정되었으며CH1이37.5분, CH2가39.5분이소요되었으며, 온도하강에는총26.5분이소요되었다. 부분부하가적용되는경우전부하가적용되는경우에비해제어정밀도의변화폭이큰것으로나타났으며스텝모터구동방식을적용한CH2의제어정밀도가상대적으로우수한것으로나타났다. 냉각수를이용한냉각사이클영역에서소비전력은1.8 kW로냉동사이클을적용한방식에비해절반가량으로감소된것으로나타났다. 본연구는실험결과를바탕으로반도체공정용칠러의최적제어방안을제시하였다.Abstract: The characteristics of a semiconductor chiller system with EEV have been experimentally studied. Threeexperiments on temperature changes (increase and decrease), load variation, and control precision were conducted toinvestigate the operating characteristics of the semiconductor chiller. The power consumption was 8.9 kWduring increase intemperature. The required time was 37.5 min for CH1 and 39.5 min for CH2. Moreover, the time required for fallingtemperature was 26.5 min. The control precision for partial load operation was relatively low compared to that of a fullload operation. In addition, the CH2 equipped with a step motor showed better control precision. The power consumed bythe chiller for process cooling water was 1.8 kW, which was one-half of that consumed during the refrigeration cycle. Theobjective of this study is to provide an optimal control guideline for the semiconductor chiller design.

Thermal and fluid flow characteristics of a micro-channeled water-block with pass variations in 8 samples were studied. The results of a numerical analysis using ANSYS CFX-11 were compared with the results of experiments. The numerical analysis and experiments were conducted under an input power of 150 W, inlet temperature of 35°C and mass flow rates of 0.7 ∼ 2.0 kg/min. The numerical results showed reasonably good agreement, within 3–5%, with the experimental results. Also, the numerical results showed that 2-pass samples give better performance than 1-pass samples in terms of heat transfer. However, the pressure drop for 2-pass samples was relatively higher.

Excessive heat occurs during the semiconductor manufacturing process. Thus, precise control of temperature is required to maintain constant chamber temperature and also wafer temperature in the chamber. Compared to an industrial chiller, a semiconductor chiller's power consumption is very high due to its continuous operation for a year. Considering the high power consumption, it is necessary to develop an energy efficient chiller by optimizing operation control. Therefore, in this study, a semiconductor chiller is experimentally investigated to suggest an energy-saving direction by conducting load change, controlling the temperature's rise and fall and controlled precision experiments. The experimental study shows how the cooling capacity of new model chiller rises over 30% compared to the old model chiller. The time and power consumption in the temperature rising experiments are 43 min and 8.4 kWh, respectively. The control precision is the same as ± 1°C, at 0°C, in any case. However, it appears that the new model channel's control precision improves to ± 0.5°C when the setting temperature is over 30°C.

The performance of flat-tube radiators with louvered fins was numerically investigated for different tube insertion lengths. The results of numerical analysis using CFX-11 were compared with experimental results. In this study, three types of flat-tube radiators with louvered fins were considered. An experiment was conducted to validate the numerical results. Flow rate ratio (FR) and Stotal were introduced to understand the uniformity of flow distribution easily. The results of numerical analysis revealed that the heat transfer rate and pressure drop increased as the mass flow rate increased. Further, the results showed that the heat transfer rate of sample 3 with h/D = 0.5 was higher than that of the other samples. The pressure drop increased as the insertion length toward the header part increased, and the pressure drop in the case of sample 3 appeared to be the highest. The factor Stotal showed that the uniformity of the flow distribution in the case of sample 1 with h/D = 0 was higher than that in the case of the other samples.

The thermal treatment for carbon nanotube was applied to remove the water, metal catalyst and other impurities in carbon nanotube. The surface of carbon nanotube was changed into open structure with acid treatment by mixed solution of and . The dispersion property of the functionalized and modified carbon nanotube was assessed with naked eyes by dispersing it in DMF. Carbon nanotube mixd polyurethane film was made to estimate the dispersion property by reflectance of the film with UV-Vis spectrometer. Also the internal structure of carbon nanotube was observed with SEM and TEM and thermal pyrolysis property of the carbon nanotube was measured by TGA and DSC. The surface modification of carbon nanotube by thermal and acid treatments improved the dispersion property of carbon nanotube/polyurethane mixed materials.

The objectives of this paper are to measure the heat transfer and pressure drop of the plate heat exchangers for absorption system applications. Three types of plate heat exchangers with different chevron angles are tested in the present experiment. Heat transfer and pressure drop performance of plate heat exchangers are measured in various operating conditions, and compared each other. The results show that the heat transfer rate of high theta (120°) and mixed theta plate heat exchanger increases about 118% and 98% at the solution flow rate 350 kg/h compared to that of low theta (60°), respectively. The effectiveness of high theta was evaluated about 0.53 ~ 0.85 in this experimental range. The experimental correlations of the Nu and f were developed with error bands of ±7% and ±12%.

The objectives of this paper are to study the characteristics of heat transfer and pressure drop of the micro channel heat exchangers using diffusion bonding technology. Four types of heat exchangers are designed and manufactured, which are straight type, long dot type, splited wavy type and straight double side type. Heat transfer and pressure drop performance of each heat exchangers are measured in various operating conditions, and compared each other. The results show that the (j/f) 1/3 performance of splited wavy type and long dot type increases about 10.3% and 6.1% at the Reynolds number 470 compared to that of straight type, respectively. On the other hand, (j/f) 1/3 performance of straight double side type decreases 19.7%.기호설명A s : 열전달면적 [mm 2 ] C: 열용량 [W/℃]C p : 비열 [J/kg․℃]D h : 수력직경 [mm] ff: 인자 j j: 인자 : 질량유량 [kg/h]Nu : 누셀트수△ P: 압력강하 [kPa] Q: 열전달률 [kW]Re : 레이놀즈수 T: 온도 [℃]Δ T: 온도차 [℃] U: 총괄열전달계수 [kW/m 2 ․℃]e : 유용도 †책임저자, 회원, 한국생산기술연구원 에너지설비기술지원센터 E-mail : kwonok@kitech.re.kr TEL : (041)589-8528 FAX : (041)589-8330 * 회원, 한국생산기술연구원 에너지설비기술지원센터

The object of this paper is to study on the thermal performance of a micro channel water block for computer CPU cooling. The effects of liquid flow rate, micro channel width and height on the thermal performances of water block are investigated experimentally. The water block was fabricated Al and machined with a micro milling. The water block consisted of rectangular micro channels 0.5 to 0.9 mm width and 1.5 to 4.5 mm height. The experiments were conducted using deionized water, over a liquid flow rate ranging from 0.2 to 2.0 kg/min. The base temperature and thermal resistance decrease with increasing of liquid flow rate. The increase of a channel height is more effective on the thermal resistance than the decrease of a channel width. At the flow rate of 0.7 kg/min, input power of 100 W, the base temperature and thermal resistance of sample 6 is 33℃ and 0.13 ℃/W respectively. 기호설명 C p : 비열 [J/kg․℃] D h : 수력직경 [mm] H ch : 채널높이 [mm] I : 전류 [A]△ P : 압력강하 [kPa] Q : 열전달량 [W]

The rapid thermal response(RTR) molding is a novel process developed to raise the temperature of mold surface rapidly in the injection stage and then cool rapidly to the ejection temperature by air or water. The objectives of this paper are to investigate the effect of mold temperature, pressure and thickness of micro pattern molding and to provide a optimization of RTR injection molding for micro pattern from Moldflow simulation. Optimal minimum temperature and pressure was found without shortcut according to thickness. Filling percentage was influenced by glass transition temperature with the kinds of resin. Optimal temperature is slightly higher than glass transition temperature irrespectively of pressure, thickness, the kinds of resin in the micro pattern molding.

Rapid mold heating has been recent issue to enable the injection molding of thin-walled parts or micro/nano structures. Induction heating is an efficient way to heat a conductive workpiece by means of high-frequency electric current caused by electromagnetic induction. Because the induction heating is a convenient and efficient way of indirect heating, it has various applications such as heat treatment, brazing, welding, melting, and mold heating. The present study covers an experimental investigation on the rapid heating using the induction heating and rapid cooling using a vortex tube in order to eliminate an excessive cycle time increase. Experiments are performed in the case of a steel cup mold core with various heating and cooling conditions. Temperature is measured during heating and cooling time, from which appropriate mold heating and cooling conditions can be obtained.