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Steam is the most energy efficient, reliable and flexible way to transfer heat within most food processing operations. This chapter discusses the differences between plant, filtered and clean steam and the various issues that affect their quality and purity. It summarises the best practices in steam system design, operation and maintenance that will help prevent contamination problems affecting food quality in the future. Food manufacturers should take pains to identify and control potential steam system contamination.

The pressure drop of a moisture separator in a steam generator is the important design parameter to ensure the successful performance of a nuclear power plant. The moisture separators have a wide range of operating conditions based on the arrangement of them. The prediction of the pressure drop in a moisture separator is challenging due to the complexity of the multi-dimensional two-phase vortex flow. In this study, the moisture separator test facility using the air/water two-phase flow was used to predict the pressure drop of a moisture separator in a Korean OPR-1000 reactor. The prototypical steam/water two-phase flow conditions in a steam generator were simulated as air/water two-phase flow conditions by preserving the centrifugal force and vapor quality. A series of experiments were carried out to investigate the effect of hydraulic characteristics such as the quality and liquid mass flux on the two-phase pressure drop. A new prediction model based on the scaling law was suggested and validated experimentally using the full and half scale of separators. The suggested prediction model showed good agreement with the steam/water experimental results, and it can be extended to predict the steam/water two-phase pressure drop for moisture separators.

R1234yf is characterized by low global warming potential (GWP) and it is a very promising candidate to substitute traditional refrigerant in the near future. The condensation heat transfer of low GWP refrigerant R1234yf was experimentally studied in detailed in this study. The influence of tube diameter was also discussed. HTCs were measured in horizontal tubes with the inner diameter (ID) of 2 and 4 mm, and the flow patterns taken during experiment were used to analyze the results. Different effects including mass fluxes, vapor quality, thermophysical properties, flow pattern and tube diameter on the HTC were also analyzed. Under the same mass flux and vapor quality, the flow patterns within ID 4 mm and 2 mm are significantly different. The turbulence between the vapor and liquid interface become gentle within ID 2 mm compared that within ID 4 mm by observation. At high mass fluxes, the HTCs within ID 2 mm tube are close to or even higher than that within ID 4 mm tube. When reducing the tube diameter, the influence of thermophysical properties, especially the surface tension on heat transfer is more obvious. Based on the laminar liquid film analytical solution and single phase forced convective heat transfer correlation, also considering the influence of surface tension and gravity, a new heat transfer correlation is developed with the experimental data using R1234yf, R134a and R32 within tube inner diameter 2 mm. The comparison shows that the mean deviation is 13.5%.

Steam-assisted-gravity-drainage (SAGD) is currently an effective technology for heavy oil recovery. The pre-heating stage is important to affect the overall process of SAGD development. In this paper, flow and heat transfer model in vertical well section and horizontal well section and thermal connectivity judgment model during cyclic pre-heating stage were established. Model calculation results are in good agreement with actual measurement results. The effects of steam injection rate and steam quality on the distribution of steam parameters along the whole wellbore and the distribution of heat transfer were compared. Besides, the optimization of steam injection parameter combination was provided. Ultimately, the effect of horizontal well spacing on pre-heating thermal connectivity was discussed. The results show that: With the increase of steam injection rate and steam injection quality, the pressure and temperature drop of the fluid increase. Wellhead required steam injection pressure and temperature increases and even superheated steam appear with the increase of steam injection rate and steam injection quality. The position where the pre-heating backflow turns from wet steam to subcooled water gradually shifts to the wellhead. With the increase of steam injection rate and steam injection quality, the heat transfer between annulus and reservoir decreases, but the uniformity of pre-heating in the horizontal section increases. The time required for cyclic pre-heating to form thermal communication between double wells increases significantly as the horizontal well spacing increases. To simultaneously integrate the uniformity and economy of pre-heating on the oilfield site, the steam injection quality at the heel end of the horizontal section of 0.7, the steam injection rate of 80 t/d, and the horizontal well spacing of 5 m were recommended.

This study performs the comparative analysis of R32 and R410A boiling inside a 4.2 mm ID microfin tube. The experimental tests were carried out at different saturation temperatures, different vapour qualities, heat fluxes and mass velocities to evaluate the specific contribution of each operating parameter. The boiling heat transfer coefficients show a great sensitivity to heat flux and vapour quality and no sensitivity to refrigerant mass velocity. The microfin tube exhibits a maximum heat transfer enhancement with respect to the smooth tube around 1.8−1.9 at a heat flux of 12 kW m−2 and a vapour quality of 0.8, and in general the heat transfer enhancement is lower than the mere surface area increase over the smooth tube (Rx= 1.65). R32 exhibits boiling heat transfer coefficients and frictional pressure drops 10 − 20% higher than those of R410A and it seems a valuable low GWP substitute for R410A.

This paper presents an experimental study of two-phase R134a flow in the inlet header of brazed plate heat exchangers and its effect on flow distribution among the channels. Visualization of the two-phase flow is accomplished through a 3-D printed transparent window on the inlet header of the heat exchangers. The two-phase flow distribution among channels is quantified based on infrared images of the heat exchanger sidewalls. At the test conditions, the observed flow regimes in the inlet header are periodic and two or three stages are identified in one cycle: top corner vapor flow, vapor jet flow, and (conditional) liquid blockage flow. Among them, the top corner vapor flow affects the distribution most, in which the vapor refrigerant is mainly present at the top corner of the header and branches out through the first several channels, leaving the liquid refrigerant to occupy the rest flow area of the inlet header and present a single-phase like distribution profile. When the inlet vapor quality increases, the distribution of the liquid refrigerant is improved since the vapor refrigerant can reach more downstream channels to help balance the total pressure drop. With the mass flux increases, the maldistribution caused by the header induced pressure drop is more significant, which compromises the benefit brought by the higher vapor momentum. When the number of plates is increased, the liquid refrigerant distribution is worse due to an increased pressure drop in the headers.

The present study investigates experimentally heat transfer of the forced convection boiling of a R134a/nano oil mixture in a horizontally-aligned tube with an aluminum helical fin. The effects of various parameters including refrigerant mass flow, vapor quality, star-shaped fin, oil concentration and volume fraction of nanoparticles are studied. SiO2–TiO2 nanoparticles are synthesized by applying both ultra-sound irradiation and sol–gel methods. Morphology and size of nanostructures are portrayed through the exact use of scanning electron microscopy, while the phase of the product is investigated by an X-ray diffraction pattern (XRD). The findings indicate that as the mass flow enhances, the heat transfer coefficient rises. The heat transfer coefficient and pressure drop have increased by using a helical fin. Regarding the oil-refrigerant mixture, the heat transfer coefficient augments at low vapor quality and reduces at high vapor quality. By adding nanoparticles, heat transfer increases, but a decreasing trend in heat transfer is observed from a certain vapor quality. The highest percentage of increase in heat transfer at a mass velocity of 380 kg/m2.s is for the case with a fin and a mixture of R134a/nano oil, and this amount is equal to 89%.

This paper presents the experimental results of saturated two-phase flow ammonia in a vertical shell and tube heat exchanger comprising of seven dimpled enhanced tubes. The tests were conducted for a wide range of parameters. The heat load was provided by hot ethylene glycol/water solution flowing on the shell side. Saturation temperature of ammonia was -20°C ≤ T sat ≤ 2°C, heat flux range 5 kW m−2 ≤ q ˙ ≤ 45 kW m−2, exit vapor quality range 0.1 ≤ x ≤ 0.9 and a mass flux range of 34.99 kg m−2 s−1 ≤ G ≤ 66.32 kg m−2 s−1. For each saturation temperature, the effects of heat flux and mass flux were studied for the saturated temperature range while the exit vapor quality at each mass flux was varied between 0.2 and 0.9. Two phase heat transfer coefficient increased with saturation temperature and heat flux. For all experimental conditions, performance showed initial increase and then a classic drop at the onset of dry out. The dimple tube showed better heat transfer coefficient compared to the previous studies performed on plain tubes with ammonia.

This study quantitatively compares the finite element (FE) and lumped modeling techniques to analyze phase-change and multiphase flow in a microchannel evaporator. We compare the one- and two-zone models in the lumped modeling approach by considering both pressure drop and phase change in the evaporator. The study investigates the deviation in results from the lumped model relative to the FE model for various evaporator heat loads. For the one-zone model, the relative errors in predicting the average density, pressure, temperature, and vapor quality increase with the evaporator heat load. This increase is mainly due to the nonlinear variation in the heat transfer coefficient and pressure drop, which are calculated with higher inaccuracies at larger evaporator heat loads. On the other hand, the liquid-phase region and the exit vapor quality are predicted more accurately. The overall errors using one- and two-zone lumped models were less than 30% when the exit qualities do not exceed 0.5. Since strategies involving flow boiling in evaporators typically avoid high exit vapor qualities to circumvent dry-out and critical heat flux, the use of lumped models under these conditions is favorable. This approach also avoids the computational costs associated with FE models while achieving sufficient accuracy to predict the evaporator’s performance.

The two-phase flow patterns of ammonia in different scale channels are experimentally investigated in this study. The inner diameters of the tested tubes are 4 mm and 8 mm. The observed flow patterns in the two tubes include slug flow, stratified-wavy flow, annular flow, and annular flow with partial dryout. For both 4 mm and 8 mm tubes, the annular flow gradually expands to a wider vapor quality range with a rise in mass flux and a descent in saturation temperature at the cost of other flow patterns. The comparison of the flow patterns in the two tubes shows that the 8 mm tube has a wider range of annular flow. This is attributed to that the higher dominance of the surface tension force in the 4 mm tube is conductive to the liquid slug to holdup on the channel wall and consequently delay the transition to annular flow. The flow patterns in the two tubes have been compared to the flow pattern maps of Baker, Mandhane et al., and Wojtan et al.. The Wojtan et al. flow pattern map could give a superior prediction for the flow patterns in the 4 mm tube, whereas none of the three existing models accurately predict the flow patterns in the 8 mm tube.

The operational performance of small-scale refrigeration systems is mainly decided by their capillary tubes outlet parameters, wherein an accurate determination of the pressure and vapour quality is a prerequisite. Experiments have been performed for a capillary tube (CT) with specified geometry consisting of a straight, a helical and a suction line heat exchanger (SLHX) section. The capillary tube is incorporated in a small refrigeration system operated with R600a. In addition, a model was developed to determine the steady-state operation of the capillary tubes (activated with R134a, R1234yf, R1234ze(E), R600, R600a, R152a and R513A refrigerants) and validated. The highest and lowest value of the vapour quality was discerned to be 0.3132 (for R1234yf) and 0.2124 (for R600), respectively. The relative errors between the experimental and model results for the CT outlet pressure and temperature were ranged from 1.16 to 5.35% and 0.12–0.81%, respectively. It is asserted that the present strategy may contribute towards the precise estimation of the pressure and vapour quality to customize the working performance of small scale refrigeration systems.

R450A is one of R134a substitutions owing to its low GWP and similar refrigeration performance. The existing researches are mostly about its performance in refrigeration systems. This paper focuses on its heat transfer characteristics in condensation. By combining the SST k-ω model with the VOF method, the condensation of R450A, and its two components, R134a and R1234ze(E), in mini-channels were explored. The mass flux ranges from 400 to 800 kg•m−2•s−1. The vapor quality is between 0.4 and 1. The tube diameters are 1mm and 2mm. The results show when the mass flux is 400, 600, and 800 kg•m−2•s−1, HTC of R134a is 11.3%-16.3%, 7.5%-15.3%, and 8.2%-14.7% higher than that of R450A, and HTC of R1234ze(E) is 5.2%-12.0%, 4.9%-12.5%, and 6.7%-14.1% higher than that of R450A. Moreover, their film thickness and axial velocity are also compared. When the vapor quality is 0.5, 0.7, and 0.9, compared with the average liquid film of R450A, that of R1234ze(E) is 1.2%, 8.8%, and 11.1% thinner and that of R134a is 4.4%, 3.6%, and 1.0% thicker, respectively. The effects of vapor quality, mass flux, channel diameter, and fluid property on the condensation of R450A are also analyzed.

R1234ze(E) and R1234yf, as green refrigerants, have received more and more attention in recent years. To better understand the performance of the evaporator working with a refrigerant/lubricating oil mixture, the solubilities of R1234ze(E)/POE85 and R1234yf/POE85 were measured using the isochoric saturation method in the temperature range from 278.15 K to 348.15 K. The NRTL model was used to correlate the new data. Using the new data, the pressure-enthalpy-vapor quality diagram and superheat-non-evaporation diagram were presented. The results show that the enthalpies of refrigerant/lubricating oil are always lower than those of pure refrigerant. The critical vapor quality is related to the refrigerant/oil solubility and oil circulation mass ratio. The enthalpy change ratio is directly proportional to the superheat and inversely proportional to the oil circulation mass fraction. The non-evaporation quality decreases as the superheat increases and increases as the mass fraction of oil circulation increases.

This paper presents an experimental and numerical investigation of the transient refrigerant and oil distribution in a residential heat pump water heater (HPWH) system. In the experiments, R134a is paired with POE 22 oil. The quick closing valve technique (QCVT) is used to trap the refrigerant and oil in each section of the system. The trapped refrigerant mass is measured after recovered by liquid nitrogen. The retained oil mass in each section, except for the compressor, is determined by the mix and sample technique (MST). Five experiments are conducted to cover a full warm-up of five hours. The experimental data shows that most of the refrigerant is in the heat exchangers. During the water warm-up, the inventory of the refrigerant generally decreases in the evaporator, while in the condenser, it decreases in the first three hours and later increases. The measurements also indicate that most of the oil stays in the compressor and the escaped oil is mainly retained in the heat exchangers. Besides, a model is developed to predict the refrigerant and oil retention in the heat exchangers by applying the mixture vapor quality to calculate the void fraction. The developed model predicts the refrigerant inventory in the condenser with an average deviation of 7.4%, and in the evaporator, 9.1%. The average deviations in the predictions of the oil retention in the two heat exchangers are 15.8% and 10.2%.

The two-phase frictional pressure drop characteristics of flow boiling in zigzag channels of the printed circuit heat exchangers (PCHEs) under different conditions were investigated experimentally. The research results show that, the friction factor f of zigzag channel is increased by 9%~17% than that of the straight channel; as the vapor quality increases, the frictional pressure drop initially increases and then decreases, reprensting a maximum value at vapor quality of 0.9; the frictional pressure drop always decreases with the increasing saturated pressure when the void fraction is higher than 0.90, and it increases with the increasing heat flux due to the larger average vapor quality and the smaller average pressure. A new correlation for the frictional pressure drop of flow boiling in PCHEs was developed within a deviation of ±25%.

In this study, we investigated the R-1234yf distribution from a header into mini-channel tubes located in a horizontal plane, which may be of importance for cooling of an electric vehicle battery. Especially, the focus was concentrated on the effect of number of branch tubes on the two-phase distribution. The tests were conducted for the mass flux from 49 to 147 kg/m2s and inlet quality from 0.2 to 0.8. The effect of heat exchanger inclination was also investigated. The results showed that the flow distribution worsened as the number of branch tube increased. Between the normal and the parallel inlet configuration, the normal inlet yielded a better distribution, probably due to the smaller number of branch tubes. The flow distribution was mainly governed by the balance of relating forces-momentum and gravitational. Thus, a poor distribution was obtained for a tilted case, where the momentum and the gravitational forces were assisting. The data showed that a vapor quality was always beneficial to the distribution. However, the effect of mass flux was case-dependent. For the horizontal case, the mass flux pushed the flow downstream, and worsened the distribution. For the tilted case, the mass flux assisted or opposed the gravity, yielding a better distribution.

This article reports on a numerical study conducted to predict the flow boiling dynamics, heat and mass transfer, and pressure drop in corrugated plate heat exchangers. The conservation equations a...

The literature survey reveals that the studies on evaporation of an alternative refrigerant for R-404A are lacking. In this study, four R-404A alternative refrigerants - two short term refrigerants (R-448A, R-449A) and two long term refrigerants (R-455A, R-454C) - including R-404A were tested in a 7.0 mm O.D. microfin tube. The tests were conducted changing the mass flux from 90 to 300 kg m−2s−1, heat flux from 5 to 15 kW m−2 and vapor quality from 0.2 to 0.8. During the test, the saturation temperature was maintained at 10 °C. The heat transfer coefficients of R-404A were higher than those of the alternative refrigerants. However, the difference tended to decrease as the mass flux increased. The higher heat transfer coefficient of R-404A may be due to the smaller temperature glide of R-404A as compared with those of other refrigerants. The microfin / smooth tube heat transfer enhancement ratios of the alternative refrigerants ranged from 1.14 to 1.93. With the mixture correction, pure refrigerant correlations successfully predicted the mixture refrigerant data.

Flow boiling experiments in microchannels under low mass fluxes have rarely been reported in the literature. In this study, flow boiling critical heat flux (CHF) for a parallel straight copper microchannel heat sink with 41 channels and hydraulic diameter of 420 µm (width: 300 µm; height: 700 µm) is reported under low mass fluxes(< 100 kg/m2s). The flow patterns reveal that the inertial force will be too low to flush the bubble downstream. The heat transfer coefficient was observed to decrease with an increase in the heat flux or vapor quality, which pointed toward convective boiling dominancy inside the channels. When approaching the CHF, the vapor flowed back to the heat sink’s inlet plenum, resulting in a flow blockage, which is the main factor for the CHF occurrence.

A Numerical investigation on the influence of heater and condenser orientation and its location on steady state performance of a Two Phase Natural Circulation Loop (TPNCL) is presented. In the present study, four possible orientations are considered in TPNCL namely, Vertical Heater and Vertical Condenser (VHVC), Vertical Heater and Horizontal Condenser (VHHC), Horizontal Heater and Horizontal Condenser (HHHC) and Horizontal Heater and Vertical Condenser (HHVC). An in house MATLAB code is developed to solve the systems of equations. Homogeneous equilibrium model (HEM) is used in two phase regions. It is observed that steady state mass flow rate of the loop is significantly influenced by the developed pressure gradient in the riser and downcomer sections, as well as available vapour quality in the riser section. Moreover, it is also noticed that condenser position and orientation significantly effects the thermo-hydraulic characteristic of loop compared with heater orientation.

The quality of steam produced by boilers is strictly standardized and must be maintained whatever the quality of makeup water and whatever the composition of the boiler unit’s thermal cycle equipment. Under the conditions of constantly improved instruments for chemical monitoring, it becomes possible to develop measurement systems using which the main standardized and diagnostic steam quality indicators can be monitored by measuring the electric conductivity and pH of cooled samples. Unlike boilers operating at a pressure of 13.8 MPa and higher, steam boilers for steam pressures equal to 9.8 and 3.9 MPa—and also industrial heat recovery steam generators—operate with steam that has a higher content of salts and carbon dioxide; in addition, it contains ammonia, which enters into steam from boiler water. Steam quality is often estimated using the two-quadrant nomographic chart of Mostofin, who proposed it more than 50 years ago. In using certain computation algorithms, it is possible to calculate the standardized and diagnostic steam quality indicators, such as concentrations of sodium, chlorides, ammonia, carbon dioxide, and salt content. The article presents an algorithm for estimating the concentrations of the above-mentioned impurities for cooled live steam samples of power-generating boilers operating at pressures below 10.0 MPa, and boilers for superhigh and supercritical pressures, and industrial heat recovery steam generators, including the combined-cycle power plant units. Examples of using the calculation procedure for analyzing the steam quality in industrial boilers are given.

To obtain the dynamic characteristics of reactor secondary circuit under transient conditions, the system analysis program was developed in this study, where dynamic models of secondary circuit were established. The heat transfer process and the mechanical energy transfer process are modularized. Models of main equipment were built, including main turbine, condenser, steam pipe and feedwater system. The established models were verified by design value. The simulation of the secondary circuit system was conducted based on the verified models. The system response and characteristics were investigated based on the parameter transients under emergency shutdown and overload. Various operating conditions like turbine emergency shutdown and overspeed, condenser high water level, ejector failures were studied. The secondary circuit system ensures sufficient design margin to withstand the pressure and flow fluctuations. The adjustment of exhaust valve group could maintain the system pressure within a safe range, at the expense of steam quality. The condenser could rapidly take out most heat to avoid overpressure.

In present work, numerical simulation has been performed using the volume of fluid method under steady-state condition to find the effect of various operating parameters, viz. mass flux, vapor quality and effective thermal conductivity on heat transfer coefficient using refrigerants R1234ze and R1234yf. The numerical simulation has been carried out using various turbulence models, viz. the standard k − e model, the standard k − ω model and the low-Re SST k − ω model. The model having minimum deviation with experimental results is considered for subsequent study. The hydraulic diameter and length of mini-channel considered are 1.085 and 420 mm, respectively. The vapor quality has been varied from 0.14 to 0.95, and mass flux has been varied from 200 to 800 kg/m2 s keeping saturation temperature of 313 K. The heat transfer coefficient results of hydrofluoroolfine refrigerants R1234yf and R1234ze have been compared with hydrofluorocarbons refrigerant R134a in order to check the suitability of new hydrofluoroolfine refrigerants as a replacement to hydrofluorocarbons refrigerant. It has been observed from the flow regime map proposed by Sardesai et al. (Chem Eng Sci 36:1173–1180, 1981) that majority results of heat transfer coefficient for refrigerants R1234ze and R1234yf fall in the annular flow regime. It has been observed that the effective thermal conductivity may play vital role in the local heat transfer rate compared with the liquid film thickness.

The heavy oil reservoirs are currently mainly targeted by thermal enhanced oil recovery technologies, particularly, steam flooding. Steam flooding is carried out by introducing heat into the reservoir to unlock the recovery of heavy oil by reducing oil viscosity. Several investigations were carried out to improve oil recovery by steam flooding. Most recently, high steam flooding is reported as an effective approach to improve recovery in high pressure heavy oil reservoirs. The oil recovery from steam flooding is substantially affected by the steam quality and injection temperature. In this study, an attempt was made to look into the integration of parameters, i.e. steam quality and injection temperature upon steam flooding on oil recovery by using a simulation approach via ECLIPSE. The results obtained indicated that high temperature along with the moderate value of steam quality gives the best result regarding oil recovery for steam flooding in an economical way.

Separation of water from steam water mixture in a WHB system is an important function of “demisters” where downstream equipment have stringent steam quality requirement in the range of 99.5% to 99.9%. Demister is a porous blanket of wires used to retain the liquid droplets carried by the vapour. Steam quality at demister outlet depends on separation efficiency of the demister. Various authors developed a number of equations to determine this separation efficiency after carrying out experimental and mathematical analysis. In this paper, a comparative study and thorough analysis of these equations is carried out for selecting appropriate correlation of demisters based on desired application. Demister efficiency of a demister with a thickness of 100 mm, wire diameter varying from 0.15 mm to 0.5 mm is determined. Pressure range is 20 bars a-140 bars a and droplet diameters of 5µ, 10µ, 20µ, 30µ, 50µ and 100µ. Wire Material is SS304L. It is observed that demister efficiency is 99.99% at low pressures (∼below 60 bars a) irrespective of the droplet diameter, and it reduces with increasing pressure. The demister efficiency reduces significantly beyond ∼ 80 bars a. It is observed that for steam with droplets less than 10µ & at low pressures; correlations provided by Oliveira et al. gives conservative efficiency. For droplets greater than 10µ diameter, both Calvert and Mohebbi et al. correlations can be used. At light steam loads and separation of less than 5µ droplet diameters, 0.09 mm to 0.15 mm diameter demister mesh wire provides better results, whereas, at high vapour loads the wire diameter of 0.15 mm to 0.25 mm can be selected.

An experimental study of post-dryout heat transfer with the coolant R-134a was performed in a vertical round tube with upward flow. The experiments were conducted in an uniformly heated tube with an inside diameter of 10 mm and a heated length of 3100 mm, at pressures of 11.1 bar, 16 bar and 28 bar, with varying mass flux in the range of 300–1500 kg/m2s. The results show that for higher mass fluxes and higher heat fluxes the wall temperature decreases after reaching a peak close to the critical vapor quality, while at lower mass fluxes the wall temperature keeps increasing after dryout. The phenomenon described last is shifted to even lower mass fluxes with rising pressure. Furthermore, it was found that at increasing pressure as well as at increasing mass flux the dryout location is shifted to lower equilibrium vapor qualities. Based on the experimental results and existing prediction methods, a theoretical model was developed to describe the heat transfer in the post-dryout area. It divides the post-dryout area into a developing and a developed region. A correction factor was introduced to model the droplet distribution in the cross-section of the fully developed region. A comparison with selected post-dryout heat transfer models from the literature for the experimental parameter range in the present study shows a good applicability of the new model.

Condensation heat transfer of R1234yf inside smooth and microfin tube with 2.5 mm outer diameter are studied experimentally. The experiments are carried out at a saturation temperature of 20°C and 30°C, mass velocity ranging from 50 to 200 kg m−2s−1 and vapor quality ranging from 0-1. The effects of mass velocity, vapor quality, and saturation temperature on condensation heat transfer coefficient are analyzed with R1234yf and R134a. Condensation heat transfer correlation for smooth tube is developed considering present experimental data and other researchers’ data. Correlation is developed using experimental data for 2.5 mm to 10 mm outer diameter tubes and refrigerants are R134a, R1234yf, R123 and R1234ze (E) by including other researchers’ data. Newly developed correlation is successfully predicted experimental data and other sources data within mean deviation of 15 %. Experimental data are also compared with previous correlations proposed for smooth and microfin tube.

Generation of air conditioners’ refrigerants suitable for countries with high ambient temperatures has become a necessity. Along with that, in this work, a non-azeotropic mixture (R-1270/R-600a), which is suitable for high ambient temperatures, composed of propylene (85%) and isobutane (15%) by mass was proposed. The heat transfer coefficient (HTC) and the frictional pressure gradient (FPG) of the boiling flow of this mixture were experimentally measured in a smooth horizontal tube and compared with that of R-22. Besides, the effect of mass flux (76.51, 95.64, and 114.76 kg/m2. s) and vapor quality (ranged from 0.1 to 0.7) on HTC were investigated. As a result, HTCs varied proportionally to both the vapor quality, and saturation pressure. Whereas, FPGs changed proportionally to vapor quality and inversely to saturation pressure. Additionally, at mass flux of 95.6 kg/m2 s, HTCs, and FPGs were enhanced by (19.04–67.32%), and (14.55–103.76%), respectively, w.r.t R-22. Moreover, the experimental results of HTCs and FPGs showed a good agreement with those of empirical correlations prediction.

This study presents an experimental investigation on the pumped two-phase cooling system designed for battery thermal management. The experimental system was established with R1233zd as the refrigerant, and a dummy battery was used to simulate the heat generation during battery operation. The thermodynamic cycle, wall temperature distribution of the cold plate and overall heat transfer coefficient were analyzed under steady state, while the transient response of the system with pump control was also studied. Results showed that the evaporating pressure of the system was not sensitive to the refrigerant mass flux, while it could be raised under higher heating loads. Both the refrigerant mass flux and vapor quality at the cold plate outlet showed little influence on the wall temperature distribution of the cold plate, however their effects on the overall heat transfer coefficient were different. An optimum value of vapor quality at cold plate outlet could be found for the pumped two-phase cooling system to achieve a maximum heat transfer coefficient. Based on this feature, a pump control program was designed and embedded into the system, and transient experiment showed that the control program could effectively handle the sharp increase of heating load. The application of the control program could lead to a near 10 K decrease in wall temperatures of the cold plate by maintaining the outlet vapor quality of the cold plate at 0.25 when the heating load was instantly raised from 100 W to 600 W, meanwhile the growth of wall temperature was also slower. The results of this study can serve as a guideline for the application of pumped two-phase cooling system on battery thermal management.