Pub Date : 2021-01-18DOI: 10.1142/s2010132521500036
M. Shaker, M. Abd-Elhady, M. A. Halim
The world is now living in an energy crisis. Refrigeration and air-conditioning systems have become the basics of daily life in various fields and accordingly, it cannot be dispensed. Refrigeration machines and air-conditioning systems are the most energy-consuming systems, independent on the application whether it is domestic, commercial, industrial or medical. Therefore, using cooling systems which are powered by thermal energy, e.g., solar energy, can save a lot of electrical energy. Absorption refrigeration system is an example of a refrigeration system powered by heat energy. However, the system problem here is that it has low coefficient of performance (COP). The objective of this research is to improve the COP of the ammonia absorption cycle. This is done in the absorber unit by improving the absorption of the refrigerant ammonia into the ammonia–water solution. The absorption efficiency is improved by using (1) a stirrer pump to improve mixing, (2) sprayers to increase the contact area between ammonia and ammonia–water solution and (3) continuous cooling of the solution during the absorption process via an external heat exchanger. The COP of the ammonia absorption cycle has increased from 0.48 to 0.715, i.e., by 49%. This is due to the improvement of the absorption of the ammonia into the ammonia–water solution.
{"title":"A Novel Technique for Improving the Performance of Ammonia Absorption Refrigeration Cycle","authors":"M. Shaker, M. Abd-Elhady, M. A. Halim","doi":"10.1142/s2010132521500036","DOIUrl":"https://doi.org/10.1142/s2010132521500036","url":null,"abstract":"The world is now living in an energy crisis. Refrigeration and air-conditioning systems have become the basics of daily life in various fields and accordingly, it cannot be dispensed. Refrigeration machines and air-conditioning systems are the most energy-consuming systems, independent on the application whether it is domestic, commercial, industrial or medical. Therefore, using cooling systems which are powered by thermal energy, e.g., solar energy, can save a lot of electrical energy. Absorption refrigeration system is an example of a refrigeration system powered by heat energy. However, the system problem here is that it has low coefficient of performance (COP). The objective of this research is to improve the COP of the ammonia absorption cycle. This is done in the absorber unit by improving the absorption of the refrigerant ammonia into the ammonia–water solution. The absorption efficiency is improved by using (1) a stirrer pump to improve mixing, (2) sprayers to increase the contact area between ammonia and ammonia–water solution and (3) continuous cooling of the solution during the absorption process via an external heat exchanger. The COP of the ammonia absorption cycle has increased from 0.48 to 0.715, i.e., by 49%. This is due to the improvement of the absorption of the ammonia into the ammonia–water solution.","PeriodicalId":13757,"journal":{"name":"International Journal of Air-conditioning and Refrigeration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2021-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88591819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-08DOI: 10.1142/s2010132521500024
H. M. Gurudatt, G. Narasimham, B. S. Gowda
Numerical simulation of a mini-channel, flat-tube, louvered fin, automotive condenser is performed to study the heat rejection rate, pressure drop and performance of the heat exchanger. The simulation study is carried out for the refrigerant R1234yf. The properties of R1234y are obtained from REFPROP software. The moist air properties are calculated from those of dry air and water vapor using suitable correlations. To select the input data, the cycle performance is carried out for a standard vapor compression refrigeration system working with R1234yf between the temperature limits of [Formula: see text]C on the low-pressure side and [Formula: see text]C on the high-pressure side. The condensation process is taken into account in three sections, namely, the superheated, two-phase and the subcooled regions. A custom code is prepared in MATLAB to solve the simultaneous equations of heat transfer from refrigerant to inside tube wall, inside tube wall to outside tube wall and outside tube wall to moist air. The simulation results show the sensible heat transfer during desuper heating to be very small compared to the condensing region. Results are reported for the pressure variation along the refrigerant flow passage in the desuper heating, two-phase and subcooling regions. The heat-transfer coefficient is found to be the highest in the two-phase region for higher dryness fractions. The effect of inlet air velocity is less compared to that of the inlet air temperature on the heat rejection rate.
{"title":"Performance of a Flat-Tube Louvered-Fin Automotive Condenser with R1234yf","authors":"H. M. Gurudatt, G. Narasimham, B. S. Gowda","doi":"10.1142/s2010132521500024","DOIUrl":"https://doi.org/10.1142/s2010132521500024","url":null,"abstract":"Numerical simulation of a mini-channel, flat-tube, louvered fin, automotive condenser is performed to study the heat rejection rate, pressure drop and performance of the heat exchanger. The simulation study is carried out for the refrigerant R1234yf. The properties of R1234y are obtained from REFPROP software. The moist air properties are calculated from those of dry air and water vapor using suitable correlations. To select the input data, the cycle performance is carried out for a standard vapor compression refrigeration system working with R1234yf between the temperature limits of [Formula: see text]C on the low-pressure side and [Formula: see text]C on the high-pressure side. The condensation process is taken into account in three sections, namely, the superheated, two-phase and the subcooled regions. A custom code is prepared in MATLAB to solve the simultaneous equations of heat transfer from refrigerant to inside tube wall, inside tube wall to outside tube wall and outside tube wall to moist air. The simulation results show the sensible heat transfer during desuper heating to be very small compared to the condensing region. Results are reported for the pressure variation along the refrigerant flow passage in the desuper heating, two-phase and subcooling regions. The heat-transfer coefficient is found to be the highest in the two-phase region for higher dryness fractions. The effect of inlet air velocity is less compared to that of the inlet air temperature on the heat rejection rate.","PeriodicalId":13757,"journal":{"name":"International Journal of Air-conditioning and Refrigeration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90398849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-05DOI: 10.1142/s2010132520500352
Oday S. Mahmood, A. Karim, S. G. Yahya, Itimad D. J. Azzawi
Ordinary refrigeration systems such as vapor-compression refrigerators are the commonly used devices in industry, mostly for their high efficiencies. However, they make a significant contribution to the depletion of Ozone and global warming due to their operational refrigerants. Hence, thermoacoustic refrigeration can be a great alternative candidate which uses inert gases such as air, helium and nitrogen as the primary refrigerant. Thermoacoustic refrigerators convert the acoustic power (sound waves) into a thermal effect (cooling power). Thermoacoustics can be counted as a new technology that has a strong potential toward the development of the thermal applications. This study aims to design and fabricate miniaturized traveling wave thermoacoustic refrigerator which can be driven by an ordinary loudspeaker. The optimized numerical design of the refrigerator shows an overall efficiency (cooling power over input electricity) of nearly 66% at a temperature difference of 25[Formula: see text]K (between cold and ambient heat exchangers). The maximum estimated cooling power is 65[Formula: see text]W at coefficient of performance (COP) of 2.65.
{"title":"Miniaturized Traveling-Wave Thermoacoustic Refrigerator Driven by Loudspeaker: Numerical Design","authors":"Oday S. Mahmood, A. Karim, S. G. Yahya, Itimad D. J. Azzawi","doi":"10.1142/s2010132520500352","DOIUrl":"https://doi.org/10.1142/s2010132520500352","url":null,"abstract":"Ordinary refrigeration systems such as vapor-compression refrigerators are the commonly used devices in industry, mostly for their high efficiencies. However, they make a significant contribution to the depletion of Ozone and global warming due to their operational refrigerants. Hence, thermoacoustic refrigeration can be a great alternative candidate which uses inert gases such as air, helium and nitrogen as the primary refrigerant. Thermoacoustic refrigerators convert the acoustic power (sound waves) into a thermal effect (cooling power). Thermoacoustics can be counted as a new technology that has a strong potential toward the development of the thermal applications. This study aims to design and fabricate miniaturized traveling wave thermoacoustic refrigerator which can be driven by an ordinary loudspeaker. The optimized numerical design of the refrigerator shows an overall efficiency (cooling power over input electricity) of nearly 66% at a temperature difference of 25[Formula: see text]K (between cold and ambient heat exchangers). The maximum estimated cooling power is 65[Formula: see text]W at coefficient of performance (COP) of 2.65.","PeriodicalId":13757,"journal":{"name":"International Journal of Air-conditioning and Refrigeration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89853768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-25DOI: 10.1142/s2010132521300019
M. Rasti, J. Jeong
Heat pump tumble dryers, air-vented dryers and condenser dryers are widely used as clothes dryers. Clothes dryers use hot air to absorb moisture from textiles to get them dry after a wash by passing drying air through the drum. To simulate the drying process of clothes in the drum and to obtain the moisture evaporation rate, it is necessary to use an accurate model to predict the moisture transfer coefficient from the textile to the air in the drum as well as the mass transfer area between the drying air and the textile. In this study, a comprehensive review of the literature on the prediction of the moisture evaporation rate inside the drum of a clothes dryers was conducted. It was found that researchers generally used constant values, fitting models, dimensionless correlations, and Chilton–Colburn analogy to predict the area–mass transfer coefficient. Moreover, few researchers used the effectiveness model for the prediction of moisture evaporation rate. The comprehensive review of the literature showed that all of the previous models for prediction of the moisture evaporation rate have some limitations in terms of generality or accuracy. Therefore, the development of a new accurate model for prediction of the moisture evaporation rate inside the drum of clothes dryers is crucial.
{"title":"A Review of Models for Estimation of Moisture Evaporation Rate from Clothes Inside a Clothes Dryer","authors":"M. Rasti, J. Jeong","doi":"10.1142/s2010132521300019","DOIUrl":"https://doi.org/10.1142/s2010132521300019","url":null,"abstract":"Heat pump tumble dryers, air-vented dryers and condenser dryers are widely used as clothes dryers. Clothes dryers use hot air to absorb moisture from textiles to get them dry after a wash by passing drying air through the drum. To simulate the drying process of clothes in the drum and to obtain the moisture evaporation rate, it is necessary to use an accurate model to predict the moisture transfer coefficient from the textile to the air in the drum as well as the mass transfer area between the drying air and the textile. In this study, a comprehensive review of the literature on the prediction of the moisture evaporation rate inside the drum of a clothes dryers was conducted. It was found that researchers generally used constant values, fitting models, dimensionless correlations, and Chilton–Colburn analogy to predict the area–mass transfer coefficient. Moreover, few researchers used the effectiveness model for the prediction of moisture evaporation rate. The comprehensive review of the literature showed that all of the previous models for prediction of the moisture evaporation rate have some limitations in terms of generality or accuracy. Therefore, the development of a new accurate model for prediction of the moisture evaporation rate inside the drum of clothes dryers is crucial.","PeriodicalId":13757,"journal":{"name":"International Journal of Air-conditioning and Refrigeration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77524252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-25DOI: 10.1142/s2010132521500012
M. Salhi, Dounia Chaatouf, Benyounes Raillani, N. Dihmani, S. Amraqui, M. Moussaoui, A. Mezrhab, J. Fontaine
This work is a contribution to the improvement of the thermal and the dynamic fields of a natural convection indirect solar dryer, composed of a solar flat air heater and a drying chamber, intended for drying agricultural products and medicinal plants. We have studied the effects of size and position of the outlet on the distribution of air and temperature within the drying chamber, containing the figs as a product to be dried. To be more realistic, we have used a user defined function (UDF) subroutine written in [Formula: see text] to integrate the unsteady evolution of a day’s climate data in the Oujda region. This study was achieved by numerical simulations using the ANSYS FLUENT software, in order to optimize the distribution of air and temperature inside the drying chamber, and to choose the best outlet’s position and size for the best efficiency of the dryer. The results show that the optimal outlet position found is in the right corner with a size range of 0.07 to 0.15[Formula: see text]m. The effects of the position and size of the outlet on the air deflection along the trays were also presented and discussed.
{"title":"Numerical Analysis of the Dynamic and Thermal Behavior of an Indirect Solar Dryer: Effect of the Outlet","authors":"M. Salhi, Dounia Chaatouf, Benyounes Raillani, N. Dihmani, S. Amraqui, M. Moussaoui, A. Mezrhab, J. Fontaine","doi":"10.1142/s2010132521500012","DOIUrl":"https://doi.org/10.1142/s2010132521500012","url":null,"abstract":"This work is a contribution to the improvement of the thermal and the dynamic fields of a natural convection indirect solar dryer, composed of a solar flat air heater and a drying chamber, intended for drying agricultural products and medicinal plants. We have studied the effects of size and position of the outlet on the distribution of air and temperature within the drying chamber, containing the figs as a product to be dried. To be more realistic, we have used a user defined function (UDF) subroutine written in [Formula: see text] to integrate the unsteady evolution of a day’s climate data in the Oujda region. This study was achieved by numerical simulations using the ANSYS FLUENT software, in order to optimize the distribution of air and temperature inside the drying chamber, and to choose the best outlet’s position and size for the best efficiency of the dryer. The results show that the optimal outlet position found is in the right corner with a size range of 0.07 to 0.15[Formula: see text]m. The effects of the position and size of the outlet on the air deflection along the trays were also presented and discussed.","PeriodicalId":13757,"journal":{"name":"International Journal of Air-conditioning and Refrigeration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87193178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-25DOI: 10.1142/s2010132520500339
Thiago Torres Martins Rocha, S. I. D. M. Resende, Hélio Augusto Goulart Diniz, F. A. R. Filho, Raphael Nunes de Oliveira
In this work, the performance of an existing algebraic solution for adiabatic coiled capillary tubes, in subcritical cycles, is investigated. However, the C-M&N friction factor, commonly used, was replaced by Schmidt friction factor, which is less complex. Two existing dimensionless correlations were also evaluated for comparison. To assess the effect of altering the friction factor, experimental data collected in the literature were used as reference. Analyzing the present results and that with C-M&N friction factor, it was observed that adopting the Schmidt friction factor does not cause a relevant impact on the solution. The deviations of the predicted versus experimental mass flow rates were comprised in a range between –8% and 12%, with average deviation (AD), absolute average deviation (AAD) and root mean square (RMS) error of –0.1%, 2.7% and 3.4%, respectively. The empirical correlations presented unsatisfactory results, with maximum deviation around 40%. Therefore, it was concluded that using the Schmidt friction factor is adequate to reduce the complexity of the algebraic solution and to maintain the accuracy.
{"title":"Assessment of a Simpler Friction Factor in an Algebraic Solution for Adiabatic Coiled Capillary Tubes","authors":"Thiago Torres Martins Rocha, S. I. D. M. Resende, Hélio Augusto Goulart Diniz, F. A. R. Filho, Raphael Nunes de Oliveira","doi":"10.1142/s2010132520500339","DOIUrl":"https://doi.org/10.1142/s2010132520500339","url":null,"abstract":"In this work, the performance of an existing algebraic solution for adiabatic coiled capillary tubes, in subcritical cycles, is investigated. However, the C-M&N friction factor, commonly used, was replaced by Schmidt friction factor, which is less complex. Two existing dimensionless correlations were also evaluated for comparison. To assess the effect of altering the friction factor, experimental data collected in the literature were used as reference. Analyzing the present results and that with C-M&N friction factor, it was observed that adopting the Schmidt friction factor does not cause a relevant impact on the solution. The deviations of the predicted versus experimental mass flow rates were comprised in a range between –8% and 12%, with average deviation (AD), absolute average deviation (AAD) and root mean square (RMS) error of –0.1%, 2.7% and 3.4%, respectively. The empirical correlations presented unsatisfactory results, with maximum deviation around 40%. Therefore, it was concluded that using the Schmidt friction factor is adequate to reduce the complexity of the algebraic solution and to maintain the accuracy.","PeriodicalId":13757,"journal":{"name":"International Journal of Air-conditioning and Refrigeration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87685807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-23DOI: 10.1142/s2010132520500340
K. W. Yong, P. Ganesan, E. Hamidi, S. Kazi, S. Ramesh
The present study investigates the water retention behavior in two different types of porous media, i.e., porous metal — a type of metallic foam and ideal geometry. The present study uses computational fluid dynamics (CFD) to model a decreasing water level in a reservoir consisting of a stationary porous medium beneath the water surface at initial stage. It mimics the setup of dynamics dip-testing which measures the amount of retained water for different types of fins-tubes heat exchangers. The study varies parameters like static contact angle ([Formula: see text]) and drainage velocity ([Formula: see text]). The literature review summarizes the unique water retention behaviors for different types of heat exchangers and the findings of the present study. Furthermore, the present study proposed new parameters for evaluating the structural variations in porous metal that explains the water saturation distribution in detail. The evaluation method could provide an insightful idea for performing the quality control check on metallic foam.
{"title":"The Effects of Hydrophobicity and Drainage Velocity on Water Retention Behaviour in Porous Media: A Computational Study","authors":"K. W. Yong, P. Ganesan, E. Hamidi, S. Kazi, S. Ramesh","doi":"10.1142/s2010132520500340","DOIUrl":"https://doi.org/10.1142/s2010132520500340","url":null,"abstract":"The present study investigates the water retention behavior in two different types of porous media, i.e., porous metal — a type of metallic foam and ideal geometry. The present study uses computational fluid dynamics (CFD) to model a decreasing water level in a reservoir consisting of a stationary porous medium beneath the water surface at initial stage. It mimics the setup of dynamics dip-testing which measures the amount of retained water for different types of fins-tubes heat exchangers. The study varies parameters like static contact angle ([Formula: see text]) and drainage velocity ([Formula: see text]). The literature review summarizes the unique water retention behaviors for different types of heat exchangers and the findings of the present study. Furthermore, the present study proposed new parameters for evaluating the structural variations in porous metal that explains the water saturation distribution in detail. The evaluation method could provide an insightful idea for performing the quality control check on metallic foam.","PeriodicalId":13757,"journal":{"name":"International Journal of Air-conditioning and Refrigeration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84745206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-20DOI: 10.1142/s2010132520500388
Dishant Sharma, G. Sachdeva, D. K. Saini
This paper presents the analysis of a modified vapor compression cooling system which uses an ejector as an expansion device. Expanding refrigerant in an ejector enhances the refrigeration effect and reduces compressor work. Therefore, it yields a better coefficient of performance. Thermodynamic analysis of a constant area ejector model has been done to obtain primary dimensions of the ejector for given condenser and evaporator temperature and cooling capacity. The proposed model has been used to design the ejector for three refrigerants; R134a, R152a and R1234yf. The refrigerant flow rate and the diameters at various sections of the ejector have been obtained by doing numerical modeling in Engineering Equation Solver (EES). Refrigerant R1234yf demanded the highest diameter requirements at a fixed 5∘C evaporator temperature and 40∘C condenser temperature for a given range of cooling load. Both primary and secondary refrigerants flow rates are higher for R1234yf followed by R134a and then R152a.
{"title":"Optimized Refrigerant Flow Rate and Dimensions of the Ejector Employed in a Modified Ejector Vapor Compression System","authors":"Dishant Sharma, G. Sachdeva, D. K. Saini","doi":"10.1142/s2010132520500388","DOIUrl":"https://doi.org/10.1142/s2010132520500388","url":null,"abstract":"This paper presents the analysis of a modified vapor compression cooling system which uses an ejector as an expansion device. Expanding refrigerant in an ejector enhances the refrigeration effect and reduces compressor work. Therefore, it yields a better coefficient of performance. Thermodynamic analysis of a constant area ejector model has been done to obtain primary dimensions of the ejector for given condenser and evaporator temperature and cooling capacity. The proposed model has been used to design the ejector for three refrigerants; R134a, R152a and R1234yf. The refrigerant flow rate and the diameters at various sections of the ejector have been obtained by doing numerical modeling in Engineering Equation Solver (EES). Refrigerant R1234yf demanded the highest diameter requirements at a fixed 5∘C evaporator temperature and 40∘C condenser temperature for a given range of cooling load. Both primary and secondary refrigerants flow rates are higher for R1234yf followed by R134a and then R152a.","PeriodicalId":13757,"journal":{"name":"International Journal of Air-conditioning and Refrigeration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88080796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-18DOI: 10.1142/s2010132520500376
S. Lowrey, G. Reboux
Small rotary compressors are used in domestic heat pump appliances, for example, in domestic dehumidifiers and heat pump clothes dryers. Compressor performance curves provided by the manufacturer can be based on testing at relatively high ambient temperatures, in some cases as high as 35∘C. This can be much higher compared with the ambient temperature in which the compressor operates when, for example, it is installed in a domestic dehumidifier which can operate in ambient temperatures as low as 10∘C. We have developed a compressor calorimeter to test a small R134a rotary compressor extracted from a commercial domestic dehumidifier and use this to measure compressor performance parameters including the isentropic and volumetric efficiencies and the compressor heat loss fraction. The performance testing has been carried out at ambient temperatures 10∘C, 15∘C, 20∘C and 25∘C for a fixed relative humidity of 70% to compare how the compressor performance varies with the ambient temperature, and to determine how well the compressor performs outside of the performance envelope provided by the manufacturer. The results show that isentropic and volumetric efficiency of these small compressors is relatively insensitive to variation in ambient temperature, even outside of the performance envelope provided by the manufacturer. However, the compressor heat loss fraction can, on average, double from 15% to 30%, between operation at ambient 25∘C and ambient 10∘C. The data obtained in this work is used to construct compressor sub-models for certain ambient temperatures. We show how these sub-models can be used to improve a domestic dehumidifier model for operation at low ambient conditions within the evaporator frosting regime and good agreement is obtained between experimental and simulated data. The authors are not aware of a domestic dehumidifier model designed to work at ambient temperatures within the frosting regime.
{"title":"Rotary Compressor Performance at Low Ambient Temperatures","authors":"S. Lowrey, G. Reboux","doi":"10.1142/s2010132520500376","DOIUrl":"https://doi.org/10.1142/s2010132520500376","url":null,"abstract":"Small rotary compressors are used in domestic heat pump appliances, for example, in domestic dehumidifiers and heat pump clothes dryers. Compressor performance curves provided by the manufacturer can be based on testing at relatively high ambient temperatures, in some cases as high as 35∘C. This can be much higher compared with the ambient temperature in which the compressor operates when, for example, it is installed in a domestic dehumidifier which can operate in ambient temperatures as low as 10∘C. We have developed a compressor calorimeter to test a small R134a rotary compressor extracted from a commercial domestic dehumidifier and use this to measure compressor performance parameters including the isentropic and volumetric efficiencies and the compressor heat loss fraction. The performance testing has been carried out at ambient temperatures 10∘C, 15∘C, 20∘C and 25∘C for a fixed relative humidity of 70% to compare how the compressor performance varies with the ambient temperature, and to determine how well the compressor performs outside of the performance envelope provided by the manufacturer. The results show that isentropic and volumetric efficiency of these small compressors is relatively insensitive to variation in ambient temperature, even outside of the performance envelope provided by the manufacturer. However, the compressor heat loss fraction can, on average, double from 15% to 30%, between operation at ambient 25∘C and ambient 10∘C. The data obtained in this work is used to construct compressor sub-models for certain ambient temperatures. We show how these sub-models can be used to improve a domestic dehumidifier model for operation at low ambient conditions within the evaporator frosting regime and good agreement is obtained between experimental and simulated data. The authors are not aware of a domestic dehumidifier model designed to work at ambient temperatures within the frosting regime.","PeriodicalId":13757,"journal":{"name":"International Journal of Air-conditioning and Refrigeration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81924580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-11DOI: 10.1142/s2010132520500364
V. Jain, Rajiv Rawat, G. Sachdeva, V. Kumar
This work conceives the performance of vapor compression cascaded refrigeration system (CRS) from the exergy, safety and thermal inventory points of view employing the theory of effective temperature ([Formula: see text] than environment temperature ([Formula: see text] in Gouy–Stodola equation. Comparative results show that the actual irreversible loss in CRS is 8.1% higher. Further, advanced exergy analysis results showed that 17.985[Formula: see text]kW irreversible loss (out of 33.737[Formula: see text]kW irreversible loss) in the system is evadable with improvement in the system design. Besides, the vulnerability of toxic fluid R717 is reported in terms of the total risk level. Moreover, the economy matter is expressed in terms of its total thermal inventory. At the base case, total risk level and total thermal inventory are determined to be 454.3 US$ and 48.86[Formula: see text]kW/K, respectively. First, sensitivity analysis is carried out to evaluate the variation in irreversible loss, total risk level and thermal inventory at different evaporator and condenser temperatures with different degrees of overlap (decision variables). A total of nine simulations are designed using the Taguchi technique. Later, multi-objective optimization is employed. The optimization process reduced the total irreversibility and annual risk level of CRS by 10.2% and 8.9%, respectively, with 6.8% increase in thermal inventory.
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