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This article presents a numerical investigation focused on how roughness of surface affects the overall performance of a counter-flow microchannel heat exchanger (CFMCHE). The study examines various microchannel shapes, including triangles, squares, circles, and trapezoids, to evaluate their performance within the context of CFMCHE. Water with consistent properties flows through aluminum microchannels used as the working fluid. The analysis employs the roughness-viscosity method to assess how surface roughness influences the CFMCHE’s performance. The study’s findings emphasize that the trapezoidal channel shape exhibits the most favorable performance among the shapes investigated. Additionally, among the operational parameters considered, the hydraulic diameter emerges as the most influential factor in determining the most suitable characteristics for CFMCHE. The presence of surface roughness was found to marginally improve thermal performance while slightly reducing hydraulic efficiency. This research provides valuable insights into the intricate interplay between surface roughness and channel shape. Notably, the impact of roughness is more pronounced in the case of the trapezoidal shape compared to other geometries. [ABSTRACT FROM AUTHOR]

[Display omitted] Experiments with dilute methane–oxygen mixtures at pressures of 100–200 Torr on the flame front propagation towards the flow of combustible gas created by a fan showed that both the mean flame velocity and the length of the 'flame jump' through a hole in a flat obstacle increase with increasing counter flow velocity; i.e. , the flame accelerates towards the counter flow of combustible gas from the fan. [ABSTRACT FROM AUTHOR]

This paper presents a numerical simulation and optimisation of a complex microchannel featuring innovative fin designs. The primary objective of the study is to minimise resistance in the heat sink by utilizing intricate fin structures. Three different approaches are explored: firstly, cylindrical solid fins are designed and placed on the heat sink; secondly, the solid fins are drilled halfway (50 %); and in the third scenario, the solid fins are drilled 87.5 % and mounted on the heat sink. In the simulation set-up, the heat sink has a heat load of 250 W imposed on the bottom wall and single-phase water of Reynolds number between 400 and 500 flows in a forced convection laminar condition to remove the heat at the bottom and internally within the fins walls surface area, while an air stream of Reynolds number between 3 and 6 flows convectively across the cylindrical fins to dissipate excess heat externally. The finite volume method and computational fluid dynamic code, are employed to discretise the geometry with heat and fluid fields solved. The optimisation is performed for parallel and counter flows and the outcomes compete favorably. Similarly, the influence of the Reynolds number on minimised temperature and resistance results is discussed. The results show that in parallel flow the integrated heat sink with half hollow fins is best with a minimised resistance of 27.2 %, while in the counter flow the hollow fins are superior with a declined resistance of 19 %. The study is validated with experimental results in open literature.

In this study, the authors investigated the environmental impact of discharging hot water from a thermal power plant into a water source for cooling. Three hundred forty-three runs using two-dimensional numerical ANSYS Fluent simulation model with (k- ε) turbulence model and open channel flow characteristics was applied in this research. The single port submerged discharge inclination angle was studied with different scenarios for the hot-water outlet (velocity and temperature) to determine the optimum inclination angle to increase cooling system efficiency and reduce hot water's environmental impact. It was discovered that by increasing the inclination angle and velocity of the hot-water outlet, the efficiency of cooling system is increased, as it increased the dilution of the hot water and reduced its environmental impact. Specifically, inclination angle of 15° increased the dilution by 80% and 86% in x and y directions, respectively compared to angle 90°. Additionally, the temperature variation in water body induced by hot-water outlet was reduced by counter flow at angle −15°. The velocity profile showed a recirculation region at the right side of the hot-water outlet, which was reduced at higher inclinations. A mathematical equation was developed to estimate the temperature value in the open channel water body based on the study parameters. Overall, the study found that increasing the inclination angle of the hot-water outlet can significantly improve the cooling system's efficiency and reduce the environmental impact of the hot water discharge. Counter flow conditions were unsuitable because they have less dilution than the normal flow conditions.

A different models of Shell-and-tube heat exchangers were designed by Ansys geometry & Solidworks to evaluate the best model for heat transfer and to calculate the difference in heat transfer in each model by investigated with numerically modeling. Each model for heat exchanger has different assumptions for first model one tube & one pass with tube length 3 meter, was made with 2 different cases (each case have the same conditions such as same temperature, same velocity, changing the direction of the flow between parallel and counter flow). The flow and temperature fields inside the shell and tubes are resolved using a Ansys CFD 17.2. A set of CFD simulations is performed for a single shell and tube bundle and is compared with the experimental results. the Realizable K-ε model is known for predicting the flow separation better than Standard K-ε. The temperature of each model is examined in detail. Each design was studied separately on the basis of the findings, the designs need modifications to improve heat transfer. The main goal of designing these models is to obtain highest performance for shell and tube heat exchanger with given conditions. These studies were carried out to find the most suitable conditions of operation in shell and tube heat exchanger so that in the future it can improve the performance of heat exchanger in industries through applying these conditions.

Widely known that, heat exchanger is a device that is being used to transfer thermal energy (enthalpy) between two or more fluids, between a solid surface and a fluid, or between solid particulates and a fluid, at different temperatures and in thermal contact. The most common heat transfer devices are concentric tube (double pipe), shell and tube and, plate heat exchanger. Nowadays, Shell and tube heat exchangers were used extensively in most industries as petrochemicals, oil and refineries. According to previous survey, almost 45% of heat exchangers utilized are shell and tube heat exchangers due to its high-pressure application it is more suitable in the field of oil & petrochemical application. Thus, the following study presented shell and tube type only. Due to complexity of studying heat exchangers experimentally, Computational Fluid Dynamics (CFD) used to simulate the effect of local surface heat transfer coefficients on the surfaces by aid of computer numerical calculation and graphical display. In addition, analysis of the physical phenomena involved in fluid flow and heat conduction would be presented in the following research paper with Comparative designs for shell and tube heat exchangers. The paper considered a review for the design of a shell and tube heat exchanger. A variety of heat exchangers are used in industry and in their products. The objective of this paper is to describe most of these heat exchangers in some detail using classification schemes and the basic design methods for two fluid heat exchangers.

A novel sample introduction and ionization method for trace explosives detection is proposed and investigated herein, taking into consideration real-world application requirements. A thermal desorption sampling method and dielectric barrier discharge ionization (DBDI) source, with air as the discharge gas, were developed. The counter flow method was adopted firstly into the DBDI source to remove the interference of ozone and other reactive nitrogen oxides. A separated reaction region with an ion guiding electric field was developed for ionization of the sample molecules. Coupled with a homemade miniature digital linear ion trap mass spectrometer, this compact and robust design, with further optimization, has the advantages of soft ionization, a low detection limit, is free of reagent and consumable gas, and is an easy sample introduction. A range of common nitro-based explosives including TNT, 2,4-DNT, NG, RDX, PETN, and HMX has been studied. A linear response in the range of two orders of magnitude with a limit of detection (LOD) of 0.01 ng for TNT has been demonstrated. Application to the detection of real explosives and simulated mixed samples has also been explored. The work paves the path to developing next generation mass spectrometry (MS) based explosive trace detectors (ETDs). [ABSTRACT FROM AUTHOR]

This paper describes experimental investigations on convective heat transfer in counter flow double pipe heat exchanger under transverse vibration for single-phase flow with twisted tape insert in the inner tube. Experiments were conducted on twisted tape inserted counter flow double pipe heat exchanger under vibration for twist ratio from 7 to 17, amplitude from 23 to 69 mm, frequency from 20 to 100 Hz and Reynolds number (Re) changing from 10710 to 21420. A maximum gain of 91% in Nusselt number (Nu) was obtained at 40 Hz frequency and 69 mm amplitude for twist ratio of 7 and Re of 10710. The maximum value of performance evaluation criteria with compound enhancement technique on double pipe heat exchanger reached 1.38 in turbulent flow conditions. Empirical correlations for Nu were developed and predicted values were found to be within ± 9% of experimental values for both frequency ranges. [ABSTRACT FROM AUTHOR]

The thermal and fluid physiognomies of a double twisted tube heat exchanger was examined numerically. Twisted engineering is a wide-use method to improve heat transfer in heat exchangers. A counter-flow mode utilizing hot water in the inner tube and cold air in the outer tube was considered. This study aims to progress the thermal performance of the double tube heat exchanger by using twisted tubes instead of plane tubes. The heat exchanger was (1m) length, outer diameter (0.05m) and inner diameter (0.025m), both with a thickness (0.004m). It was tested for different values of twist ratios (Tr= 5, 10, and 15 respectively) and Reynolds numbers (Re=5000 to 30000). The Navier - Stockes and energy equations besides the turbulence model in demand for modelling this physical problem. ANSYS Fluent code was used for the numerical simulation. The results showed that the twisted tube heat exchanger showed increasing heat transfer compared with a plain tube heat exchanger. It was found that the cold outlet temperature, pressure drop and effectiveness are increased as the twist ratio increases. [ABSTRACT FROM AUTHOR]

The application of pyrolysis for the thermal decomposition of tire waste can be taken as the ideal concept to reduce and recycle tire waste. The product of the process can produce condensate oil, a typical oil that is close to crude oil properties. The critical aspect of the pyrolysis process is the design of the reactor, particularly for the condenser where the rate of heat transfer contributes to the overall quality and quantity of the produced condensate oil. This study focused on the effect of water flow direction on the condensation process of pyrolysis gas. The quantity and quality of the produced oil are examined to observe the effect of the condensation process. Two different water flow directions are tested in the process, namely, counter flow and parallel flow direction. The effect of water flow direction in the condenser clearly affects the pyrolysis process to produce the condensate oil. Based on the production quantity, the counter flow condenser is able to produce 355 ml of condensate oil while the parallel flow one merely 290 ml. Based on the quality of the produced condensate oil, the counter flow condenser is generally better than the parallel flow one where the density, flash point and viscosity are close to crude oil properties. The rate of heat transfer from the condenser to the pyrolysis gas is the main factor that contributes to the quality and quantity of the condensate oil. The average heat transfer for the counter and parallel flow is 2,728 W and 1,865 W, respectively. It can be said that using the counter flow condenser for the pyrolysis reactor can improve the quality and quantity of the condensate oil. [ABSTRACT FROM AUTHOR]

In this paper, the condensation heat transfer characteristics of parallel flow and counter flow inside an inclined wave-finned flat tube is investigated experimentally. The condensation heat transfer coefficients are analyzed based on the experimental results. Results of experiments show that condensation heat transfer coefficient decreases as the temperature difference Δt=ts—tw increases and mass flow rate decreases. The parallel flow has a similar development with the counter flow, and the condensation heat transfer coefficient of counter flow is less than that of parallel flow under the same air cooling conditions. In addition, condensation heat transfer coefficient correlations are also obtained under experimental ranges. The calculations agree well with the measured data and the agreement is seen to be within ±4% for the parallel flow and ±5% for the counter flow. [ABSTRACT FROM AUTHOR]

The present paper is an investigation of the cooling of hot shear thinning fluids flowing through cylindrical pipes. The study is achieved via numerical simulations with the help of the computer code CFX, which is based on the finite volume method to solve the governing equations. The efficiency of two techniques for achieving the cooling process is investigated, namely: the counter flow and the baffling techniques. In the first part and for the first strategy, the hot fluids are cooled by an external turbulent counter flow of a Newtonian liquid. In the second part and in an attempt to enhance the energy efficiency of the heat exchanger system, semi-circular baffles are inserted. We note that two strategies are used in combination in the second part of study. Effects of the flow rates and the pitch ratio of the inserted baffles on the flow and thermal fields are explored. The obtained results show a great enhancement of heat transfer rates when using both strategies in combination.

There often exist behaviors of moving against the main direction of evacuation in order to rescue or find the important missing people in real situations. However, the traditional social force model (SFM) often lacks consideration of such "counter flow". Motivated by this, we improve the traditional SFM to study the counter flow and its influence on evacuation out of multi-exit rooms. We call the person to be rescued "superior" and the rescuers "subordinate". Two different rescue situations are proposed: superior waiting in place (case 1) and superior moving towards the exit (case 2). The results show that the counter flow will always reduce the evacuation efficiency to a certain extent, and the evacuation efficiency of case 1 is lower than that of case 2. At the same time, for these two cases, increasing the number of rescuers increases the evacuation time. We also find that the existence of counter flow can enlarge the effect of "faster-is-slower", while increasing the number of exports can significantly improve the rescue efficiency. We hope that this result can help to improve the efficiency of emergency evacuation with rescue. [ABSTRACT FROM AUTHOR]

In this paper, the absorbent carryover effect in a designed counter-flow enthalpy exchanger is investigated. In a built prototype of the liquid desiccant dehumidifier, air and the absorbent solution are in contact and flow through a packed multi-channel polymer tower in a counter-flow pattern. To avoid the absorbent carryover, the tower is equipped with an eliminator. Experimental measurements show that applying wick of hydrophilic type material to the channels' surfaces of the eliminator and the enthalpy exchanger, while increasing the rate of dehumidification, reduces the solution carryover effect, however, it does not eliminate it. To eliminate the effect, pumping the solution into the tower is interrupted periodically. It was found that by adjusting the pump switching frequency, the carryover effect can be eliminated. The best result is achieved when the period of switching on state is about a quarter of the off state one and the total period is about 25 seconds. Since the solution pump is turned off frequently, the cost of electrical power is reduced significantly. Also, the measurements show that while the dehumidification ability of the tower is improved in a steady state operation its regeneration performance is not.

The transfer functions G(s) for different types of heat exchangers obtained from their partial differential equations usually contain some irrational components which reflect quite well their spatio-temporal dynamic properties. However, such a relatively complex mathematical representation is often not suitable for various practical applications, and some kind of approximation of the original model would be more preferable. In this paper we discuss approximate rational transfer functions G^(s) for a typical thick-walled double-pipe heat exchanger operating in the counter-flow mode. Using the semi-analytical method of lines, we transform the original partial differential equations into a set of ordinary differential equations representing N spatial sections of the exchanger, where each nth section can be described by a simple rational transfer function matrix Gn(s), n=1,2,…,N. Their proper interconnection results in the overall approximation model expressed by a rational transfer function matrix G^(s) of high order. As compared to the previously analyzed approximation model for the double-pipe parallel-flow heat exchanger which took the form of a simple, cascade interconnection of the sections, here we obtain a different connection structure which requires the use of the so-called linear fractional transformation with the Redheffer star product. Based on the resulting rational transfer function matrix G^(s), the frequency and the steady-state responses of the approximate model are compared here with those obtained from the original irrational transfer function model G(s). The presented results show: (a) the advantage of the counter-flow regime over the parallel-flow one; (b) better approximation quality for the transfer function channels with dominating heat conduction effects, as compared to the channels characterized by the transport delay associated with the heat convection.

Membraneless microfluidic fuel cells (MMFCs) are being studied extensively as an alternative to batteries and conventional membrane fuel cells because of their simple functioning and lower manufacturing cost. MMFCs use the laminar flow of reactant species (fuel and oxidant) to eliminate the electrolyte membrane, which has conventionally been used to isolate anodic and cathodic half-cell reactions. This review article summarizes the MMFCs with six major categories of flow configurations that have been reported from 2002 to 2020. The discussion highlights the critical factors that affect and limit the performance of MMFCs. Since MMFCs are diffusion-limited, most of this review focuses on how different flow configurations act to reduce or modify diffusive mixing and depletion zones to enhance the power density output. Research opportunities are also pointed out, and the challenges in MMFCs are suggested to improve cell performance and make them practical in the near future.

• Long length HTS cables can be cooled effectively using counter flow technique. • The effect of heat flux on pressure drop is insignificant. However, heat generation could significantly affect pressure drop in HTS cables. • Fully developed velocity profiles cannot be expected due to flow through corrugated pipes. • The temperature difference between inlet and outlet of HTS cables can be kept minimum with counter flow cooling. High temperature superconducting (HTS) cables cooled with liquid nitrogen (LN 2) have been found to be most promising alternative to conventional cables for meeting the ever-rising energy demand across the world. The heat accommodated by the LN 2 flowing in HTS cable has various major sources such as AC loss in the superconductor, dielectric loss in dielectric material, and heat influx through the cryogenic enclosure wall from ambient temperature. Thus, in order to operate long length HTS cables, the thermal and hydraulic analysis of LN 2 flowing in the HTS cable is essential. However, the LN 2 flow is more complex when flowing through stainless steel corrugated pipes with counter-flow cooling arrangement. In the present work, counter-flow cooling system is considered for the analysis to reduce the highest temperature attained in the HTS cable. Moreover, the influence of various heat fluxes and heat generations on the pressure drop and heat transfer is carried out using computational fluid dynamics (CFD) approach. The two-equation turbulence model k-epsilon (k-ϵ) is used to analyze the thermohydraulic behavior of LN 2 , where the thermophysical properties of LN 2 are considered to be temperature dependent. The obtained pressure drop is compared with the experimental data of a parallel flow HTS system, fabricated in NEDO project. Consequently, the friction factor for counter flow HTS system is found to be quite larger than the parallel flow HTS system. [ABSTRACT FROM AUTHOR]

Highlights • A randomly distributed hollow fiber membrane tube bank (HFMTB) is applied. • The randomly distributed HFMTB is used for sweeping air membrane distillation (SGMD). • The conjugate heat and mass transfer in the randomly distributed HFMTB are investigated. • The friction factors, local and mean Nusselt and Sherwood numbers are obtained and validated. • Effects of the structural and transport parameters on the basic data are studied. Abstract In practical sweeping gas membrane distillation (SGMD) with hollow fiber membrane tube banks (HFMTB), the tubes are often populated in a randomly distributed configuration. The brine and the sweeping gas countercurrently flow inside and between the tubes, whereby heat and moisture exchange. Water vapor transferred through the membranes from the hot brine side to the cold gas side is taken out of the HFMTB by the sweeping gas. Conjugate heat and mass transfer in the tube bank is investigated. Three square modules consisting of 20 fibers, the brine stream inside the fibers, and the sweeping gas stream between the fibers with various randomly populated features are selected as the computational domains. The equations governing the momentum and heat mass transports in the tube side, membrane side, and shell side are established and solved based on the conjugate heat and mass transfer boundary conditions. The friction factors, local and mean Nusselt and Sherwood numbers in the modules are obtained and validated. Effects of the tube distributions, packing fractions, and moisture diffusivities in membranes on heat and mass transfer are studied. The HFMTB is recommended to be the regularly distributed one. The automatic processing of the regularly distributed HFMTB should be realized in future. [ABSTRACT FROM AUTHOR]

Highlights • An interlocking double layer counter flow channel heat sink for IGBT is proposed. • The heat sink performance predicted by the 1-D flow boiling model for counter flow. • The model analysis is performed by iterative operations by genetic algorithm. • The benefits of counter flow are uniform surface temperature and low thermal resistance. Abstract Mini and micro-channel heat sinks with two-phase flow boiling are considered as one of the promising cooling methods due to their ability to efficiently manage high heat flux heat dissipation. However, it is characterized by a significant decrease in the heat transfer coefficient of the liquid deficient portion where the quality of flow is increased by the boiling in the channel. The heat transfer coefficient at which the wall dry-out occurs sharply decreases, which can cause a large temperature gradient in the direction of flow. Such a dry-out condition may correspond to the critical heat flux state, and a drastic decrease in cooling performance is inevitable. To alleviate the temperature gradient increase and to improve the cooling performance, the two-phase counter flow mini-channel heat sink with interlocking double layer structure has been proposed. The proposed mini-channel heat sink was designed based on the commercial IGBT module size and numerically analyzed by applying 1-D two-phase flow in each counter flow direction. Two-phase boiling heat transfer correlation and momentum equation were solved to calculate the pressure drop and analyze the cooling performance benefits of proposed counter flow heat sink. The applied analysis method was extended to the single-phase counter flow situation and the results were compared with two-phase flow case. From the results of the analysis, it was confirmed that the counter flow heat sink can obtain a more uniform temperature distribution than the conventional unidirectional heat sink. The non-uniformity of the temperature distribution due to the uneven flow rate of the parallel channels can be improved by applying the counter flow configuration. [ABSTRACT FROM AUTHOR]

A comparative thermal analysis of water and engine coolant oil in a helical coil tube and shell heat exchanger is performed. The experimental study is carried out in parallel and counter flow conditions with laminar flow of the fluids. Various factors like heat transfer coefficient, friction factor, pressure drop, and pumping power for different fluid flow rates of 0.25 lpm (litre per minute), 0.5 lpm, and 0.75 lpm along tube side and shell side are compared. The other common factors of the heat exchanger along tube and shell side like overall heat transfer coefficient, NTU (Number of Transfer Units), LMTD (Log Mean Temperature Difference), effectiveness, and average heat transfer coefficient are also analysed for variation in flow rates. The variation of overall heat transfer coefficient is also compared with different non-dimensional numbers such as He (Helical Number), De (Dean Number), LMTD, and NTU. The maximum enhancement % of various heat transfer characteristics comparative to water in parallel flow condition is provided. For coolant oil in counter flow condition, the average heat transfer is enhanced by 63.3%, convective heat transfer coefficient by 42.7%, and overall heat transfer coefficient by 98.9% compared to parallel flow of water. It is also observed that counter flow of water provides more enhanced heat transfer (18.7%) than parallel flow of coolant oil. Finally it is concluded that in helical tube and shell type of heat exchanger the counter flow with coolant oil as a coolant is more effective. [ABSTRACT FROM AUTHOR]

Highlights • High-temperature heat transfer in foam filled double-pipe heat exchanger is studied. • Coupling effect between two fluid sides and the wall thickness effect are considered. • Decreasing porosity and increasing pore density improve the exchanger effectiveness. • Performance improvement is slight while dimensionless exchanger length exceeds 35. Abstract A numerical investigation is performed to analyze the high-temperature heat transfer behavior in a double-pipe heat exchanger filled with open-cell porous foam. The Forchheimer-extended Darcy equation and the local thermal non-equilibrium model are utilized to simulate the flow and thermal transport inside the foam regions, considering the coupling effects between the inner and annular spaces. The effect of solid wall thickness is incorporated in the modelling process, following the continuity conditions of temperature and heat flux at the porous-solid interface. Simulations are conducted for a counter-flow heat exchanger while the thermal radiation transfer is solved using the P1 approximation. The cold fluid flows in the inner pipe, whereas the hot fluid in the annular gap. The temperature distribution, pressure drop, heat exchanger effectiveness and the overall performance are predicted. Effects of thermal radiation, foam structural parameters and the heat exchanger size are examined. The results indicate that thermal radiation promotes the thermal exchange between the two fluid sides. The heat exchanger effectiveness is improved by decreasing the porosity or increasing the pore density, exchanger length and annulus dimension, however, the potential increase in the total pressure drop should be seriously considered. Besides, the overall performance is slightly improved by further increasing the exchanger length when the dimensionless length is greater than 35. [ABSTRACT FROM AUTHOR]

Highlights • 2-D model of crossflow IEC concerning possible condensation was developed. • The condensation behavior of cross flow and counter flow IEC were comparatively studied. • Influence of inlet air conditions on IEC performance with condensation was quantitatively analyzed. • Channel gap and height to length ratio of IEC were optimized. Abstract Indirect evaporative cooling is recognized as an alternative air-cooling solution with low carbon potential and considerable energy efficiency. An indirect evaporative cooler (IEC) can handle both of the sensible and latent cooling loads because of possible condensation when it is used as a precooling unit in an air-conditioning system in hot and humid regions. Cross flow and counter flow, as two basic flow configurations of an IEC, differ in condensation behavior that affects their cooling performance. In this paper, a novel 2-D model of cross flow IEC considering condensation is established and validated. The performance of the cross flow and counter flow IEC is thoroughly compared under the same configuration. The channel gap and height to length ratio (H/L) are optimized to provide references for the design and operation of the IEC under condensation conditions. Results show that under the same operating conditions, the condensation ratio of counter flow IEC is 2–15% higher than that of the cross flow IEC, leading to 2–7% decrease of wet-bulb effectiveness. The difference in the total heat transfer rate between the two configurations is less than 5% when the number of transfer units (NTU p) is lower than 3.1. For cross flow IEC, there is an optimal value in H/L among 0.4–0.8 considering the cooling capacity and energy consumption. [ABSTRACT FROM AUTHOR]

Liquid desiccant dehumidification, a clean energy technique for creating comfortable environments has received a lot of interest. Several dynamic models have been proposed to predict the outlet air humidity ratio and temperature, however, a study on presenting variations of heat and mass transfer coefficients and thermal mass of desiccant during the dynamic dehumidification process was not encountered according to authors' best knowledge. This gap is primarily due to the complex nature of the coupled heat and mass transfer processes, which make it challenging to capture the evolution of heat and mass transfer coefficients over time. In this study, variations of these parameters are analyzed at first. A theoretical study is conducted to show the thermal mass of the desiccant can be considered constant when changing the inlet air humidity ratio or desiccant temperature, simplifying the dynamic modeling process. While the variation of heat and mass transfer coefficients show significant impact in such conditions. Subsequently, a new method based on mass conservation is provided to determine the thermal mass of desiccant. By examining the cause-and-effect relationships between heat and mass transfer coefficients and outlet air humidity ratio, the evolution of heat and mass transfer coefficients following exponential laws is deduced by inversion. Then a dynamic model of packed dehumidifiers can be completed easily based on above derivations, and its viability is confirmed by experimental results. Compared to the existing method, the prediction accuracy can improve by 50% based on the proposed methods. This study characterizes evolution rules of heat and mass transfer coefficients over time, and with this, evolutions of outlet air parameters during the dynamic dehumidification process can be acquired conveniently based on the existing steady dehumidification model. • Variations of heat and mass transfer coefficients and thermal mass of desiccant are analyzed. • Simple methods are proposed to figure out the evolutions of thermal masses, and heat and mass transfer coefficients. • The prediction accuracy of air outlet humidity ratio could improve by 50% based on the proposed methods. [ABSTRACT FROM AUTHOR]

In this study, the authors investigated the environmental impact of discharging hot water from a thermal power plant into a water source for cooling. Three hundred forty-three runs using two-dimensional numerical ANSYS Fluent simulation model with (k- ε) turbulence model and open channel flow characteristics was applied in this research. The single port submerged discharge inclination angle was studied with different scenarios for the hot-water outlet (velocity and temperature) to determine the optimum inclination angle to increase cooling system efficiency and reduce hot water's environmental impact. It was discovered that by increasing the inclination angle and velocity of the hot-water outlet, the efficiency of cooling system is increased, as it increased the dilution of the hot water and reduced its environmental impact. Specifically, inclination angle of 15° increased the dilution by 80% and 86% in x and y directions, respectively compared to angle 90°. Additionally, the temperature variation in water body induced by hot-water outlet was reduced by counter flow at angle −15°. The velocity profile showed a recirculation region at the right side of the hot-water outlet, which was reduced at higher inclinations. A mathematical equation was developed to estimate the temperature value in the open channel water body based on the study parameters. Overall, the study found that increasing the inclination angle of the hot-water outlet can significantly improve the cooling system's efficiency and reduce the environmental impact of the hot water discharge. Counter flow conditions were unsuitable because they have less dilution than the normal flow conditions. [ABSTRACT FROM AUTHOR]

Abstract Equilibrative nucleoside transporters (ENTs), which facilitate cross-membrane transport of nucleosides and nucleoside-derived drugs, play an important role in the salvage pathways of nucleotide synthesis, cancer chemotherapy, and treatment for virus infections. Functional characterization of ENTs at the molecular level remains technically challenging and hence scant. In this study, we report successful purification and biochemical characterization of human equilibrative nucleoside transporter 1 (hENT1) in vitro. The HEK293F-derived, recombinant hENT1 is homogenous and functionally active in proteoliposome-based counter flow assays. hENT1 transports the substrate adenosine with a Km of 215 ± 34 µmol/L and a Vmax of 578 ± 23.4 nmol mg−1 min−1. Adenosine uptake by hENT1 is competitively inhibited by nitrobenzylmercaptopurine ribonucleoside (NBMPR), nucleosides, deoxynucleosides, and nucleoside-derived anti-cancer and anti-viral drugs. Binding of hENT1 to adenosine, deoxyadenosine, and adenine by isothermal titration calorimetry is in general agreement with results of the competitive inhibition assays. These results validate hENT1 as a bona fide target for potential drug target and serve as a useful basis for future biophysical and structural studies.

Abstract An Indirect Evaporative Cooler (IEC), when used as a precooling unit in the fresh air system, can achieve heat recovery through the use of exhaust air and is attractive for energy saving. In hot and humid areas, the IECs can also realize considerable latent heat recovery due to the possible condensation. Based on statistical data derived by numerical models of different types of IECs, this research developed simplified models for predicting the annual energy saving potential of IECs applied in practices in hot and humid areas. Results showed that the predicted values of simplified models can agree well with the simulated values. By integrating the fitted regression equations to building energy consumption simulation, a case study of a wet market in Hong Kong was conducted. Consequently, the IEC can achieve 43.8 ~ 56.4% energy saving to the HVAC system. [ABSTRACT FROM AUTHOR]

Highlights • A counter-flow heat pump driven liquid desiccant dehumidification system is tested. • There exists an optimal solution flow rate for the system and COP sys can be 6.5. • Appropriate air inlet parameters will have favorable effects on system performance. • Suitable supplementary water capacity is proposed to improve system performance. • COP sys of the new system can be 30% higher than the previous cross-flow system. Abstract A counter-flow heat pump driven liquid desiccant dehumidification (HPLD) system is considered as an energy-efficient approach for the humid air handling process, with advantages in terms of higher efficiency and simpler configuration. It is found that the adoption of a multi-stage heat pump cycle can improve the system performance, and then experimental tests for the system performance of the HPLD system with a two-stage heat pump cycle are investigated in the present study. The effects of solution flow rate, air inlet parameters including outdoor air and indoor exhaust air, and supplementary water capacity for the system on the system performance are elucidated according to the experimental results. It is found that the solution flow rate could affect the heat recovery performance between outdoor air and indoor exhaust air, and the performance of the heat pump. Thus, there exists an optimal solution flow rate for this counter-flow HPLD system, and the coefficient of performance of the system (COP sys) can be as high as 6.5 under the experimental condition. Besides, the increase of outdoor air inlet parameters and the decrease of indoor exhaust air inlet parameters with enough indoor exhaust air flow rate for the system have favorable effects on the system performance, due to the promotion to the heat recovery performance of the system. And more supplementary water capacity to remove the redundant heating capacity of the system would also improve the system performance mainly through lowering the condensing temperature. However, supplementary water capacity cannot be added too much for the system due to the dehumidification demand. Furthermore, the coefficient of performance of this counter-flow HPLD system is approximately 30% higher than that of a cross-flow HPLD system, handling more dehumidification demand. [ABSTRACT FROM AUTHOR]

Highlights • A counter flow double pass SAH has been proposed with two new modifications. • Installing aluminum cans to the absorbing plate for improving the heater efficiency. • Three absorbing plates were tested, flat plate, cans in aligned and staggered shapes. • Guide blades are attached to the entrance region for ensuring well air distribution. • The maximum daily efficiency was about 68%, at 0.05 kg/s for the staggered DPSAH. Abstract Performances of the new Double Pass Solar Air Heater (DPSAH) with and without turbulators has been studied experimentally in the present investigation. Aluminum cans are attached to the upper and lower surface of the absorber plate and used as turbulators to enhance the heater efficiency. Effects of aluminum cans on Nusselt number and pressure drop of SAHs have been investigated. In addition, guide blades are attached to DPSAH entrance for ensuring adequate air distribution over the surface of the absorber which in turns enhancing the performance. Each case is compared with another Single Pass Solar Air Heater (SPSAH) at the same time. The air mass flow rate range is from 0.02 kg/s to 0.05 kg/s. Three variously designed absorber plates for DPSAH are tested: (a) flat plate absorber without cans, (b) absorber with cans in aligned configuration, (c) and the third one contains cans arranged in a staggered configuration. The purpose of the aluminum cans is to create turbulence intensity in the flow field and enlarge the heat transfer area of DPSAHs; hence, and consequently enhance heat transfer rate. Results showed that the maximum daily efficiency was 68% at 0.05 kg/s for the staggered DPSAH. [ABSTRACT FROM AUTHOR]