Temperature Of Air Stream Research Articles

Microcontroller-based integrated data logging system for solar air heater performance assessment

ABSTRACT Efficiency curves for assessing solar air heater (SAH) performance are determined by measuring different parameters under certain operating conditions recommended by different test standards such as American Society of Heating, Refrigerating and Air-Conditioning Engineers. In this work, development and testing of a low cost integrated datalogging system for tracing efficiency curves are presented. Pyranometer (CMP11) and temperatures sensors (DS18B20) are integrated with microcontroller (AT89S52) for continuous data recording at desired time interval. Switching devices are integrated to automatically control operations of electric heater for maintaining inlet air stream temperature as per testing requirements. Using the system, efficiency curves of a 1.46 m2 SAH installed in Tezpur University, India, are determined at two mass flow rates of air. Results are comparable with published literatures revealing negative slope (energy loss component, F R U L ) and positive intercept (energy absorption component, F R (τα) n ) of efficiency curves. SAH shows better performance at lower mass flow rate of air (0.0235 kg/m2-s), with F R U L as 13.5 W/m2-K compared to operation at 0.0430 kg/m2-s mass flow rate of air where slope increases by around 23% with same intercept. Higher slopes of the SAH demonstrate its highest sensitivity to prevailing wind compared to three previously published designs. Present study shows that the integrated system can replace individual traditional measuring instruments for respective parameters like solar irradiance and temperatures as well as additional control equipment required to maintain desired test conditions. Further development of the system can lead to a modular and portable efficiency curve tracer for SAH performance assessment.

Modeling of Separation with Drying Processes for Compressed Air Using an Experimental Setup with Separation–Condensation and Throttling Devices

In modern industrial plants, compressed air is the most commonly used energy source; however, it is a source of condensation, which is not desirable for pneumatic equipment. This article describes a model of compressed air drying based on the principle of a refrigeration dryer. However, instead of gas refrigerants, the method proposed is to use cooled compressed air as a cooling medium with a temperature below 273 K. The main objective is to study the possibility of replacing harmful refrigerant gases with a neutral type of coolant. To carry out this research, a test bench containing a plate heat exchanger and a throttling device was designed and manufactured. This study has yielded the following scientific results. Firstly, the Joule–Thompson effect was used during the experiments, which facilitated a reduction in the temperature of the compressed air to 255 K. Secondly, using the expanded air and a plate heat exchanger, the temperature of the main compressed air stream was reduced to 280 K, which is very close to the temperature provided by standard-refrigeration-type compressed air dryers. This suggests that it is possible to use compressed air energy to cool the main stream of warm compressed air after the compressor. In general, the temperature range ensures the compressed air quality at the level of class 4 in accordance with international standards.

Landscape influences on thermal sensitivity and predicted spatial variability among brook trout streams in the southeastern USA

AbstractWarming water temperatures as a result of climate change pose a major threat to coldwater organisms. However, the rate of warming is not spatially uniform due to surface‐ground‐water interactions and stream and watershed characteristics. Coldwater habitats that are most resistant to warming serve as thermal refugia and identifying their locations is critical to regional aquatic conservation planning. We quantified the thermal sensitivity of 203 streams providing current and potential habitat for brook trout (Salvelinus fontinalis) across nearly 1000 linear km of their native range in the southern and central Appalachian Mountains region, USA, and characterized their spatial variability with landscape variables available in the National Hydrography Dataset. Using the Bayesian framework, we calculated the maximum slope of the logistic function relating paired weekly mean air temperature and stream temperature as an index of stream thermal sensitivity. Streams differed greatly in thermal sensitivity and those with more resistant water temperature regimes (i.e., thermal refugia) were consistently characterized by southerly latitudes and groundwater input. Landscape variables derived from a principal component analysis explained 16% of the variation in thermal sensitivity, indicating that the existing landscape variables were modestly successful in explaining spatial thermal heterogeneity. Using our model and spatial interpolation, we predicted thermal sensitivity at 8695 stream segments potentially suitable for brook trout in the study region. Thermal refugia were more common southward presumably due to higher elevations, but elsewhere they were also clustered at finer spatial scales. Our analysis informs prioritizing habitat conservation and restoration of this native salmonid and other aquatic organisms that depend on coldwater habitats in a warming world.

Numerical evaluation of sweeping gas membrane distillation for desalination of water towards water sustainability and environmental protection

Sweeping gas membrane distillation (SGMD) is considered a membrane distillation configuration. It uses an air stream to collect the water vapour. A 2D mathematical model is prepared in the current study to predict the effect of various operating parameters on the SGMD performance. Also, the temperature distribution in the SGMD was obtained. The effect of air inlet temperature, salt concentration, feed and air flowrate on air and salted solution outlet temperature and vapour flux through the membrane is investigated. There was good agreement between experimental data and modelling outputs. It was found that increase in air inlet temperature from 40 to 72 °C was increased the outlet temperature of air stream and cold solution from 37 to 63 °C and 38 to 65 °C respectively. Furthermore, increase in air inlet temperature led to the enhancement of vapour flux in the membrane distillation. Also, the salt concentration and feed flow rate did not have meaningful influence on the outlet temperatures, however, the flux was increased by increasing feed flowrate.

Stream groundwater inputs generate fine‐scale variation in brook trout phenology and growth across a warming landscape

Abstract Climate change is increasing global atmospheric temperatures, which can reduce abundance and cause range shifts in species that are sensitive to warming. However, fine‐scale thermal heterogeneity can drive highly variable local responses to climate change, especially in freshwater environments that differ in groundwater inputs and geomorphology. We used temperature data collected during 2012–2021 from 10 small, pristine streams in eastern Canada to characterise thermal variation at a small spatial scale (~25 km2). We then used relationships between daily air and stream temperatures to reconstruct stream temperature since 1980, and assessed how thermal variation influenced the phenology and growth of brook trout (Salvelinus fontinalis). Air–stream temperature relationships varied considerably among streams despite their close proximity, with predicted summer temperatures differing up to 9.5°C between warmer rainfall‐dominated streams and cooler groundwater‐dominated streams. Rainfall‐dominated streams warmed more than twice as fast as groundwater‐dominated streams across all seasons since 1980, with nearly four‐fold differences in rates of warming evident during summer months. Fine‐scale thermal heterogeneity also shaped brook trout phenology, as juveniles in rainfall‐dominated streams were estimated to hatch and emerge much later (~70 and 40 days, respectively) and experience faster phenological shifts than in groundwater‐dominated streams. Relationships between juvenile brook trout size and accumulated degree‐days were positive, but slopes differed over two‐fold and did not vary systematically based on stream hydrology, suggesting more idiosyncratic impacts of warming on early growth. Collectively, our study illustrates how species responses to climate change in freshwater environments can be consistent in direction but vary substantially in magnitude owing to the influence of groundwater. Future climate change is likely to increase the thermal stress experienced by brook trout populations in warmer rainfall‐dominated streams, while potentially benefiting those in groundwater‐dominated streams where current temperatures are often suboptimal. Observed differences in the rates and ecological impacts of warming among streams suggest that fine‐scale thermal variation must be considered when forecasting effects of future climate change on stream fish population dynamics.

On the energy performance of the geothermal dehumidifier of the humidification-dehumidification desalination system

The solar-driven humidification-dehumidification desalination system with a geothermal dehumidifier (SD-HDH-GD) has been given special attention, especially for subsurface irrigation. This contribution scrutinizes the performance of the geothermal dehumidifier of the SD-HDH-GD system. To this aim, a comprehensive three-dimensional transient computational fluid dynamics model of the geothermal dehumidifier and the surrounding soil is developed. An experimental setup is established to verify the developed numerical model. The effect of several operating parameters on the performance of the system is examined. The sensitivity of the water yield, recovery ratio, and gain output ratio to the studied parameters are analyzed. It is demonstrated that the system has different behaviors regarding these measures. Therefore, to gain a comprehensive understanding of the performance of the SD-HDH-GD system, all measures should be considered. According to the obtained results, the maximum amount of condensed water, gain output ratio, and recovery ratio obtained using the performed optimization are 180.05 kg/12 hours, 41.20%, and 0.31, respectively, for the open-air HDH cycle. Moreover, to reach the optimum system performance, the temperature of the inlet air stream to the geothermal dehumidifier should be in the range of 60 to 70 °C, and its relative humidity must be as much as possible.

Support Pore Structure and Composition Strongly Influence the Direct Air Capture of CO2 on Supported Amines.

A variety of amine-impregnated porous solid sorbents for direct air capture (DAC) of CO2 have been developed, yet the effect of amine-solid support interactions on the CO2 adsorption behavior is still poorly understood. When tetraethylenepentamine (TEPA) is impregnated on two different supports, commercial γ-Al2O3 and MIL-101(Cr), they show different trends in CO2 sorption when the temperature (-20 to 25 °C) and humidity (0-70% RH) of the simulated air stream are varied. In situ IR spectroscopy is used to probe the mechanism of CO2 sorption on the two supported amine materials, with weak chemisorption (formation of carbamic acid) being the dominant pathway over MIL-101(Cr)-supported TEPA and strong chemisorption (formation of carbamate) occurring over γ-Al2O3-supported TEPA. Formation of both carbamic acid and carbamate species is enhanced over the supported TEPA materials under humid conditions, with the most significant enhancement observed at -20 °C. However, while equilibrium H2O sorption is high at cold temperatures (e.g., -20 °C), the effect of humidity on a practical cyclic DAC process is expected to be minimal due to slow H2O uptake kinetics. This work suggests that the CO2 capture mechanisms of impregnated amines can be controlled by adjusting the degree of amine-solid support interaction and that H2O adsorption behavior is strongly affected by the properties of the support materials. Thus, proper selection of solid support materials for amine impregnation will be important for achieving optimized DAC performance under varied deployment conditions, such as cold (e.g., -20 °C) or ambient temperature (e.g., 25 °C) operations.

Preparation and evaluation of sustained release formulation of PLGA using a new injection system based on ink-jet injection technology

We developed a method for the preparation of PLGA particles exhibiting long-term sustained-release of entrapped drugs. The fine droplet drying (FDD) technology using a new injection system based on ink-jet injection technology was adapted as the preparation method. PLGA microspheres containing TRITC-dextran, acetaminophen, and albumin as model drugs were prepared by the FDD technology. The resultant microspheres were uniform in size, with average particle sizes ranging from 16.3 to 33.0 μm and SPAN factors ranging from 0.49 to 0.77. The encapsulation efficiency of drugs showed high values ranging from 75 to 99 wt% of the total amount of water-soluble drug contained in the particles. In an investigation of the optimal operation conditions of the FDD technology, the dew point temperature of the dryer air stream was found to be an important factor for controlling the initial burst of the prepared particles. The TRITC-dextran-containing PLGA microspheres were confirmed to exhibit long-term sustained release for about 90 days, and the mechanism was found to be PLGA degradation rate-limiting. Based on these results, we concluded that long-term sustained-released PLGA particles can be prepared by using FDD technology under a suitable drying condition for controlling the initial burst.

Energy, exergy and economic analyses of an optimal use of cryogenic liquid turbine expander in air separation units

Cryogenic liquid turbine expanders have emerged quite recently as a replacement for traditional Joule-Thomson valves in cryogenic processes for energy saving purpose. However, introducing a liquid turbine expander into the cryogenic air separation unit (ASU) can influence the operating points of ASU components, and the maximum benefits arising from the liquid turbine expander have not yet been reported. To fill such a gap, thermodynamic models are first established for ASU components, including the main air compressor, booster air compressor, cryogenic gas and liquid turbine expanders, main heat exchanger, cryogenic pump, and distillation column. To achieve the best possible use of the liquid turbine expander, an optimization method is developed by incorporating the thermodynamic models with the particle swarm optimization algorithm, in which the total minimization power consumption of ASU is the optimization goal while the flow rates and pressures of the high pressure air stream and the air stream drawn from the booster air compressor middle section together with the temperature of the medium pressure air stream exiting the main heat exchanger midway act as the optimization variables. Then, energy, exergy and economic analyses are conducted and the corresponding indexes are chosen to quantitatively evaluate the influence of the liquid turbine expander on the air separation process. For the case study, ASUs of 35000 Nm3/h oxygen production capacity with and without a cryogenic liquid turbine expander are optimized, respectively. The results show that the ASU total power saving through the use of liquid turbine expander is 4.2-fold its output shaft power; thus, the energy consumption of unit oxygen decreases by 2.12% and the overall exergy efficiency increases by 1%. In addition, the economic analysis shows that the period of return of the liquid turbine expander in the ASU is estimated to be 1.75 years.

O074 A systematic scoping review of minimally invasive respiratory monitoring

Abstract Introduction Respiratory rate (RR) is a key marker of stress with evidence that raised RR is the vital sign most predictive of cardiac events. Respiratory monitoring is critical to detecting Sleep Disordered Breathing (SDB). COVID-19 highlighted the importance of infection control, and methods of detecting RR without direct airstream contact have wide application for diagnostic and monitoring in respiratory medicine. This scoping review aims to provide an up-to-date overview of indirect respiratory monitoring. Method Systematic literature searches were conducted according to PRISMA-ScR guidelines on PubMed, Embase, ProQuest and Scopus covering articles published between January 2012, until February 2022. Data was extracted into the following categories : physiological signal, sensor type, sensor location and field of use. Analysis methods and effectiveness of each method were also assessed. Results 10736 articles were screened, 236 articles were included for analysis. 61.9% (n=146) monitored respiration through periodic motion of the chest and abdomen, 22.5% (n=53) cardiorespiratory coupling 7.6% (n=18) airstream temperature, 2.5% (n=6) respiratory sounds, 0.4% (n=) remote airflow monitoring, and 5.1% (n=12) combined markers. Medical and clinical research accounted for 42.4% (n=100) of papers, health and exercise monitoring 28% (n=66), and sleep monitoring 16.9% (n=40).22 different sensor types were identified, the most common being remote radar monitoring 17.8% (n=42), photoplethysmography 14.8% (n=35), AI assisted video monitoring 9.7% (n=23) and thermal imaging 8.5% (n=20). Discussion Indirect RR monitoring technology that is typically unutilized in clinical settings. Continued development in AI assisted signal analysis will make these methods more accessible for clinical and consumer use.

River water temperature demonstrates resistance to long‐term air temperature change

AbstractEcosystem health and water quality of rivers are dependent on their temperature. With ongoing human‐induced climate change causing increases in air temperature across the globe, it is anticipated the stream temperatures will rise too—in turn increasing the rates of biogeochemical stream processes and potentially threatening the viability and health of aquatic organisms. To understand the relationship between climate change and stream temperature response, the longer the records that can be analysed, the more the robust the analysis for detecting change. In this study, we analyse records from 263 catchments from across the United Kingdom for 45 years from 1974 to 2019 to assess the link between air temperature and stream temperature change. To give the most precise analysis of these long records, Bayesian hierarchical modelling was used and showed that: (i) The Bayesian hierarchical approach was 59% more precise, that is, reduced uncertainty on long‐term trends, than using simple linear regression. (ii) The increase in annual average air temperature over 45 years across the United Kingdom showed no significant differences between 22 weather stations and gave a 45‐year change of 1.35 ± 0.9°C. (iii) Trends in annual mean stream temperature change varied from −2.3 °C to 2.0 °C over 45 years, with the mean over 263 sites being 0.5 °C over 45 years. (iv) 1% of rivers showed a stream temperature trend significantly greater than the air temperature trend but 3% of sites showed a stream temperature trend significantly lower than zero. (v) 74% of all river sites showed no significant monotonic trend, either positive or negative, in water temperature even after 45 years. The observed declines in stream temperature could be ascribed to the closures of thermoelectric power stations but it is unclear why the stream temperature at some sites has risen faster than air temperature. The study shows that mean river temperature was well buffered against changes in air temperature—a 1°C rise in air temperature giving 0.37°C in mean stream temperature.

Optimization of a rotary desiccant wheel for enthalpy recovery of air-conditioning in a humid hospitality environment

Excessive condensation on cooling coils can be costly energy-wise due to humid process air streams. An innovative desiccant cooling system is introduced into an existing hotel in Taoyuan, Taiwan, where the ambient is humid year-round. Rejected heat from the existing cooling system is used as the energy source to heat the regeneration airstream for dehumidification of the process airstream via a rotary desiccant wheel. The paper develops and validates a numerical model for the heat and mass (moisture) transfer of the rotary desiccant wheel. The validated numerical model is used to simulate the expected performance of the rotary wheel under various conditions and operating strategies. The desiccant wheel’s performance includes the steady-state moisture removal capacity (MRC) and the transient response time to reach steady-state. The examined factors include the ambient temperature and humidity, air flow rate, rotational speed of the wheel, wheel-split, and regeneration airstream temperature. From the simulation results, the paper offers the optimized control strategies for the operation of the rotary desiccant wheel system in the hotel.

Prediction of optimum operating conditions of a furnace under uncertainty: An integrated framework of artificial neural network and genetic algorithm

The current work developed an integrated framework of artificial intelligence and genetic algorithm (GA) for the furnace of a petroleum refinery to predict the optimum amount of excess air and mass flow rates of crude oil and fuel stream in the presence of uncertainty in process conditions. A furnace model was built in Aspen Exchanger Design and Rating (EDR) using industrial data. Then interface between the furnace model and MATLAB was established using the com server. Data points were generated by varying the crude oil composition as well as the inlet temperature and pressure of cold crude oil, fuel, and air stream through ±1%, ±2%, ±3%, ±4%, and ±5% change in their original values. Then GA was used to determine the optimal amount of excess air and mass flow rates of crude oil and fuel for each data point. In total, 360 data points were generated and 70 % of the data set was utilized for training an Artificial Neural Networks (ANN) model while the remaining data points were evenly distributed for its validation and testing. The proposed ANN model achieved high performance with a correlation coefficient of 0.99984. Furthermore, exergy analysis of the standalone furnace model, the GA based optimized model, and the ANN integrated model was performed. The GA based approach outperformed the standalone model in terms of exergetic efficiency. On the hand, the ANN based framework achieved comparable exergetic efficiency to the GA based approach within significantly lesser period of time.

Drying kinetics of two fruits Portuguese cultivars (Bravo de Esmolfe apple and Madeira banana): An experimental study

Air convective dehydration was carried out at a laboratory scale using two fruits of cultivars produced in different regions of Portugal: Bravo de Esmolfe apple, from Beiras province, and Cavendish banana, from Madeira Island. Fresh fruits were dried in a tray drier with a hot airstream at different temperatures (35, 40, 45, and 50 °C) and velocity of 1.6 m s−1. Drying rate curves were obtained using a simple mathematical approach applied to the moisture content curves adjusting linear and polynomial functions. Different drying rate stages were noticed in the experiments made with apples (one constant drying rate period followed by two falling drying rate periods), while in the case of the banana the constant drying rate period was not perceived, being dried entirely during a unique falling drying rate period. As expected, the constant drying rate value obtained at the beginning of the experiments with apples is higher when these were conducted at higher temperatures, changing from 8.103 to 14.474 g m−2 s−1 when the airstream temperature increases from 35 to 50 °C. The correspondent critical moisture contents in the Bravo de Esmolfe apples, at the instant the constant drying rate period stops and the drying rate starts to fall, slightly decreases from 4.800 to 4.134 kgwater/kgdry solid.This study explored for the first time the drying behavior of these two important fruits that have been increasingly used in the food industry in Portugal, giving important information for the industrialization of its production.

A Dynamic Simulation Model for a Heat Exchanger Malfunction Monitoring

Modelling and simulation is presented for a finned cross-flow heat exchanger with the aim to heat cold air to be fed to air conditioning batteries for marine purposes. The model employed in this paper is finalized to simulate the dynamic behavior of air and water temperatures fed to the air conditioning batteries operating in cold environments, in order to predict possible troubles owing to the change in input parameters, such as unwanted flow rate variations due to system malfunctions. In the investigated model, heat balance equations are presented and discretized by Laplace transform, which has the advantage to easily account for the different structures of heaters used for the purpose of validation. The model was implemented in the Matlab-Simulink environment for its high capacity of dealing with dynamic systems. The results of the model are satisfactory, as the dynamic behavior of the air stream temperature is correctly reproduced, as compared to experimental data, providing a suitable parameter for malfunctions prediction.

Coupling terrestrial and aquatic thermal processes for improving stream temperature modeling at the watershed scale

Water temperature is an important indicator of the health of terrestrial and aquatic ecosystems and influences numerous biological and chemical processes that affect water quality, the health and productivity of biota, and other ecosystem services. In this study, we improved the Soil and Water Assessment Tool (SWAT) model to explicitly consider the thermal processes influencing the temperature of various terrestrial water components (i.e., surface runoff, lateral flow, and base flow) and the heat balance of water in streams. The improved SWAT model with an explicit heat balance description on both terrestrial and aquatic thermal processes (SWAT-HB) was compared with previous versions of the SWAT model that employ only empirical relationships between air temperature and stream temperature (SWAT-ER) or combine empirical terrestrial water temperature estimates with the heat balance of stream water (SWAT-EH) for the Upper Mississippi River Basin (UMRB) and Greensboro Watershed (GW) in the United States. The results show that, even though the SWAT-HB better simulates terrestrial thermal processes, all three models produce comparable simulations of long-term stream temperatures, indicating that stream temperature is mainly influenced by air temperature as water travels along large rivers. Nevertheless, the SWAT-HB and SWAT-EH models achieved better performance than the SWAT-ER model in the winter and spring but exhibited mixed performance in the summer and fall. The better model performance of the SWAT-HB model than the SWAT-EH model can be attributed to the improved estimation of terrestrial water temperature components. Although, empirical methods (e.g., SWAT-ER) are suitable for providing estimation of stream temperature, the coupled terrestrial and aquatic heat balance-based methods (e.g., SWAT-HB) allow for the consideration of land and water management practices (e.g. crop irrigation, land use change, and water use for thermoelectric cooling) effects on stream temperature.

Experimental methods to determine the performance of desiccant coated fixed-bed regenerators (FBRs)

Desiccant coated fixed-bed regenerators (FBRs) transfer heat and moisture between two airstreams having different temperature and humidity. The experiments on FBRs are challenging because of their transient nature of operation. Unlike other energy exchangers, FBRs do not attain a steady-state condition; instead, they reach a quasi-steady state where the humidity and temperature of the outlet air continuously vary with time. This paper shows that measuring the temperature and humidity of a time-varying airstream with temperature and humidity sensors may lead to errors in the effectiveness in the order of 15–20%. Meanwhile, the method proposed in this paper reduces errors to ±5–8%, which is comparable to the accepted uncertainties in steady-state test standards. The major contributions of this paper are: (i) development and verification of new experimental methods to determine the effectiveness of desiccant coated FBRs and (ii) verification of the bag sampling method (BSM) for humidity measurements proposed by test standards. The results are verified using a validated numerical model and a correlation from the literature.

Thermal effectiveness of wind-tower with heated exit-wall and inlet-air humidification: Effects of winter and summertime

Wind-towers provide natural ventilation to residential building in hot arid and semi-arid climate. Water-droplet spray can reduce the air-stream temperature at air-inlet section to increase wind-tower effectiveness. However, temperature and humidity weather conditions due to climate change throughout the year play a main role. Besides, heating of building's structure produced by solar radiation has an impact on interior air-stream temperature. This paper presents a thermal assessment of combined wind-tower air-humidification with a heated wall under the effect of winter and summertime. A correlation Nusselt-Reynolds numbers for different weather conditions was developed experimentally, which investigates thermally a simulated solar heating of an exit-wall wind-tower-building by means of a parallel plate heat exchanger tested in a low-speed wind tunnel. The effect of a water-droplet spray on the wind-tower streams and constant heating exit-wall of the building was investigated varying the air-inlet Re number between 1.3x104 and 2.5x104. The results show that Nu number increases with Re number for both dry-air and moist-air flow wind-tower-building inlet condition. Wind-tower thermal effectiveness is 11.6% higher for summertime compared to the wintertime. Results for dry-air and moist air and the Nu-Re correlation can be used as guidelines for future wind-tower designs.

Energetic and exergetic performance comparison of an experimental automotive air conditioning system using refrigerants R1234yf and R134a

In this study, the energetic and exergetic performance merits of an automotive air condition-ing (AAC) system using R134a and R1234yf have been investigated. For this aim, a laboratory AAC system was developed and equipped with devices for mechanical measurements. The refrigeration circuit of the system mainly had an evaporator, condenser, liquid receiver, fixed capacity compressor, and thermostatic expansion valve. The tests were performed by changing the compressor speed and air stream temperatures incoming the condenser and evaporator. Based on energy and exergy analysis, various performance parameters of the AAC system for both refrigerants were determined and presented in comparative graphics. It was found that R1234yf resulted in 0.4–10.9% lower refrigeration capacity, 5.5–11.6% lower COP, and 4.7–16.1°C lower compressor discharge temperature, while yielding 9.3–22.3% higher refrig-erant mass flow rate and 1.1–3.5°C higher conditioned airstream temperature in comparison to R134a. Moreover, the components of the R1234yf system usually destructed more exergy, and the total exergy destruction rate per unit refrigeration capacity of the R1234yf system was 4.1–15.3% greater than that of the R134a one.

Numerical analysis of cross-flow plate type indirect evaporative cooler: Modeling and parametric analysis

This paper focuses on numerical modeling of heat and mass transfer characteristics within a plate type cross-flow indirect cooling system considering the impact of the surface wettability factor. For this objective, a numerical model is developed to implement the heat and mass transfer process calculations inside the indirect cooling system. The mathematical model validated by published data from literature with a perfect convention. To specify the parameters that significantly affect the indirect evaporative cooling system’s performance, precise analysis is executed by employing three evaluation indexes, including the average outlet temperature of the product air stream, cooling capacity rate, and wet-bulb efficiency. The simulation results showed that the surface wettability factor greatly influences the performance of IECs. Moreover, improving the wettability factor has a positive influence on enhancing the cooling capacity and wet-bulb efficiency. When the wetting factor is increased from (0.5–1.0) the wet-bulb efficiency increased from 69% to 92%, respectively, and the average outlet temperature decreased from 27 °C to 24 °C. Furthermore, the heat and mass transfer performance strongly relies on the air inlet temperature, the intake velocity, mass flow rate, and working air humidity ratio.