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Calibration Strategies And Limitations Of Cycle Simulations Representing Complex Domestic Cooling Devices, Martin Heimel, Erwin Berger, Stefan Posch, Johann Hopfgartner, Stephan Schlemmer, Raimund Almbauer Jan 2016

Calibration Strategies And Limitations Of Cycle Simulations Representing Complex Domestic Cooling Devices, Martin Heimel, Erwin Berger, Stefan Posch, Johann Hopfgartner, Stephan Schlemmer, Raimund Almbauer

International Refrigeration and Air Conditioning Conference

Transient cycle simulations are commonly said to be a tool for improving and understanding the operating behavior of cooling cycles. Assuming a properly working simulation tool, simple cycle configurations which are driven by On/Off-controlled compressors can meanwhile be modelled with relatively high effort. Given the growing complexity of today's modern refrigeration appliances – in particular cooling/freezing combinations – it is getting more and more challenging to represent these in a satisfactory manner. Fans for ventilation, variable speed drives and switchable capillary tubes are in interaction and follow a sensor-controlled, prescribed logic. The focus of this paper lies on the simulation …

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Numerical Simulation Of The 3d Transient Temperature Evolution Inside A Domestic Single Zone Wine Storage Cabinet With Forced Air Circulation, Johann Hopfgartner, Martin Heimel, Stefan Posch, Erwin Berger, Raimund Almbauer, Stephan Schlemmer Jan 2016

Numerical Simulation Of The 3d Transient Temperature Evolution Inside A Domestic Single Zone Wine Storage Cabinet With Forced Air Circulation, Johann Hopfgartner, Martin Heimel, Stefan Posch, Erwin Berger, Raimund Almbauer, Stephan Schlemmer

International Refrigeration and Air Conditioning Conference

This work is carried out in order to investigate the air flow and temperature stratification in the compartment of a single zone wine storage cabinet with forced ventilation for domestic use. The appliance used in this work has a total gross capacity of approximately 135 liters. A single zone wine cooler should achieve evenly distributed temperature for all bottles inside the appliance. To analyze the temperature distribution, a numerical simulation of the air flow and the temperature field can be very helpful. The numerical simulations are carried out applying commercial CFD (Computational Fluid Dynamic) software using the finite volume method. …

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Automated Optimization Of Air Conditioning Systems Using Geometry Based Simulation Models, Joerg Aurich, Rico Baumgart, Eric Tomoscheit Jan 2016

Automated Optimization Of Air Conditioning Systems Using Geometry Based Simulation Models, Joerg Aurich, Rico Baumgart, Eric Tomoscheit

International Refrigeration and Air Conditioning Conference

The major topics of current developments in the household appliance industry are cost reduction and the optimization of energy efficiency. For that purpose mathematical simulation models are increasingly used. However, most of these models are based on measurements. Hence, a geometrical optimization of the refrigerant cycle components is practically impossible. If physical based models are used optimization is mostly done manually by varying individual geometric properties. Due to the large amount of parameters and possible combinations a determination of the optimal parameter set is not possible. Moreover, each parameter combination requires a separate setting of the overall system and the …

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Modeling Of Finned-Tube Heat Exchangers: A Novel Approach To The Analysis Of Heat And Mass Transfer Under Cooling And Dehumidifying Conditions, Hongtao Qiao, Christopher R. Laughman Jan 2016

Modeling Of Finned-Tube Heat Exchangers: A Novel Approach To The Analysis Of Heat And Mass Transfer Under Cooling And Dehumidifying Conditions, Hongtao Qiao, Christopher R. Laughman

International Refrigeration and Air Conditioning Conference

The construction of physics-based models of the simultaneous heat and mass transfer on the air-side surface of air-cooled fin-and-tube heat exchangers during dehumidification can present distinct challenges. Because only part of the external surface of a finite length finned tube may be wetted in the radial and/or axial directions, the determination of the wet/dry boundary for this partially wet tube surface must parsimoniously describe the nonlinear variations in both the refrigerant temperature and air temperature profiles. A literature review indicates that extant heat exchanger models tend not to consider the partially wet conditions due to modeling complexity; moreover, many standard …

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Development Of An Embedded Rtu Fdd Using Open-Source Monitoring And Control Platform, Andrew L. Hjortland, James E. Braun Jan 2016

Development Of An Embedded Rtu Fdd Using Open-Source Monitoring And Control Platform, Andrew L. Hjortland, James E. Braun

International Refrigeration and Air Conditioning Conference

Previous research on automated fault detection and diagnostics (FDD) for HVAC systems has shown promising benefits like earlier detection and more accurate isolation of different faults. While most researchers, equipment manufacturers, and policymakers agree that HVAC system FDD is important and has the potential to reduce significant energy waste due to faulty system operation, widespread adoption of these tools has been slow. An automated fault detection and diagnosis system has been developed for packaged (rooftop) air conditioners based on the VOLTTRONTM monitoring and controls framework developed by the Department of Energy. The system implements a virtual-sensor-based FDD methodology capable of …

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Second-Law Analysis To Improve The Energy Efficiency Of Environmental Control Unit, Ammar M. Bahman, Eckhard A. Groll Jan 2016

Second-Law Analysis To Improve The Energy Efficiency Of Environmental Control Unit, Ammar M. Bahman, Eckhard A. Groll

International Refrigeration and Air Conditioning Conference

This paper presents a second-law of thermodynamics analysis to quantify the exergy destruction in each component of an Environmental Control Unit (ECU) for military applications. The analysis is also used to identify the potential con- tribution from each component to improve the overall energy efficiency of the system. Three ECUs were investigated experimentally at high ambient temperature conditions to demonstrate the feasibility of the model presented herein. The investigated ECUs have capacities of 1.5 (5.3 kW), 3 (10.6 kW), and 5 (17.6 kW) tons of refrigeration (RT). The results indicate that the largest potential to improve exergetic efficiency of each …

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Optimized On-Off Controller For Energy Saving In A Household Refrigerator, Ulisses Carvalho De Elian Saffar, Antônio Augusto Torres Maia Jan 2016

Optimized On-Off Controller For Energy Saving In A Household Refrigerator, Ulisses Carvalho De Elian Saffar, Antônio Augusto Torres Maia

International Refrigeration and Air Conditioning Conference

The domestic refrigerator is responsible for 30% of the average household electricity consumption in Brazil, and the power costs regarding a single refrigerator represents up to 5% of the Brazilian minimum wage. The capacity control method employed in most of these systems consists of a thermostat used to turn on and off the compressor to maintain the temperature between the desired levels. This method of capacity control is responsible for efficiency losses as a result of the start-up and shut-down transients. The duration and the number of on/off cycles influence directly the temperature profile inside the refrigerator and the system …

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Analysis Of The Drop-In Operation Of A Refrigeration System By The Response Surface Methodology, Victor Hugo Panato, Marcus Almeida Queiroz, Luis Manoel Paiva Souza, Arthur Heleno Pontes Antunes, Enio Pedone Bandarra Filho Jan 2016

Analysis Of The Drop-In Operation Of A Refrigeration System By The Response Surface Methodology, Victor Hugo Panato, Marcus Almeida Queiroz, Luis Manoel Paiva Souza, Arthur Heleno Pontes Antunes, Enio Pedone Bandarra Filho

International Refrigeration and Air Conditioning Conference

The objective of this study is to evaluate the gains in a drop-in process of refrigerants in a basic refrigeration system using the Response Surface Methodology to optimization. A central composite design and analysis of variance are also used. In addition, the model will be analyzed and compared to experimental results, consolidating various parameters to get the best regions in a broad universe of options, with a reduced number of experiments. The response surface methodology is a set of statistical tool, which describes the entire region of interest through experimental specific points, by appropriate polynomial equation. The experimental results were …

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A Novel Model Considered Mass And Energy Conservation For Both Liquid And Vapor In Adsorption Refrigeration System., Tsung Yi Lin, Chien Chang Wu, Tsung Lin Chen Jan 2016

A Novel Model Considered Mass And Energy Conservation For Both Liquid And Vapor In Adsorption Refrigeration System., Tsung Yi Lin, Chien Chang Wu, Tsung Lin Chen

International Refrigeration and Air Conditioning Conference

In this paper, we proposed a dynamic model for a two-bed adsorption refrigeration system. Different from most existing researches which assume saturation vaper pressure in each device, the proposed method models the pressure in each device by considering both the liquid and vaper content in the device. Therefore, it can be more accurate in describing the system response and more suitable for studying the system instrumentation. The components included in this system model are: adsorption bed, evaporator, condenser, expansion valve, and etc. Each device is modeled based on the energy and mass conservation. Furthermore, the adsorption phenomenon is modeled by …

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Method For Determining Air Side Convective Heat Transfer Coefficient Using Infrared Thermography, Scott S. Wujek, Wayne L. Staats, Stefan W. Elbel, Jeffrey P. Koplow, H. Arthur Kariya, Predrag S. Hrnjak Jan 2016

Method For Determining Air Side Convective Heat Transfer Coefficient Using Infrared Thermography, Scott S. Wujek, Wayne L. Staats, Stefan W. Elbel, Jeffrey P. Koplow, H. Arthur Kariya, Predrag S. Hrnjak

International Refrigeration and Air Conditioning Conference

Air side convective heat transfer coefficients are among the most important parameters to know when modeling thermal systems due to their dominant impact on the overall heat transfer coefficient. Local air side convective heat transfer coefficients can often prove challenging to measure experimentally due to limitations with sensor accuracy, complexity of surface geometries, and changes to the heat transfer due to the sensor itself. Infrared thermography allows local heat transfer coefficients to be accurately determined for many different surface geometries in a manner which does not impact the results. Moreover, when determining convective heat transfer coefficients for a large number …

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Numerical Modelling Of Heat And Mass Transfer Processes In Chinese Cabbage Cold Storage Chamber, Miroslawa Kolodziejczyk, Dariusz Butrymowicz, Kamil Smierciew, Jerzy Gagan Jan 2016

Numerical Modelling Of Heat And Mass Transfer Processes In Chinese Cabbage Cold Storage Chamber, Miroslawa Kolodziejczyk, Dariusz Butrymowicz, Kamil Smierciew, Jerzy Gagan

International Refrigeration and Air Conditioning Conference

During storage of fruits and vegetables in cold stores, quantitative as well as qualitative losses may occur due to non-uniformity of storage conditions. The macroscopic energy balance, mainly used to design storage chambers, cannot predict where storage conditions are going to induce the loss of commodity. The numerical modelling of the cold storage can be applied as an effective tool to investigate the  homogeneity of the treatments to which the produce is subjected. The most important factors affected the uniformity of temperature and relative humidity, and consequently, the quality of the commodity, are velocity, temperature and humidity of air …

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Experimental And Numeric Quantitative Evaluation Of Thermal Performance In Refrigerated Display Cabinets With Variation Of Air Curtain Thickness And Porosity Of The Back Panel, Samuel Mariano Nascimento, Gustavo Galdi Heidinger, Pedro Dinis Gaspar, Pedro Dinho Silva Jan 2016

Experimental And Numeric Quantitative Evaluation Of Thermal Performance In Refrigerated Display Cabinets With Variation Of Air Curtain Thickness And Porosity Of The Back Panel, Samuel Mariano Nascimento, Gustavo Galdi Heidinger, Pedro Dinis Gaspar, Pedro Dinho Silva

International Refrigeration and Air Conditioning Conference

The use of computational tools for engineering troubleshooting and new product development has increased significantly in recent years. Computational Fluid Dynamics is used in the field of commercial refrigeration for more than 10 years for the development and improvement of equipment. Vertical open multideck refrigerated display cabinets (VORDC) are widely used to expose perishables in supermarkets and convenience stores. This paper reports the numerical results of a series of CFD simulations of a VORDC to predict the best air mass flow between the discharge air grille (DAG) and the perforated back panel (PBP) and also the relationship of air mass …

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Investigations Of Low Pressure Two-Phase Steam-Water Injector, Roman Kwidzinski, Dariusz Butrymowicz, Jaroslaw Karwacki, Marian Trela, Kamil Smierciew Jan 2016

Investigations Of Low Pressure Two-Phase Steam-Water Injector, Roman Kwidzinski, Dariusz Butrymowicz, Jaroslaw Karwacki, Marian Trela, Kamil Smierciew

International Refrigeration and Air Conditioning Conference

Vapor-liquid injector is a passive device in which thermal energy of vapor is used to compress and heat a cold liquid. In the past such injectors were used extensively for feeding water into boilers, especially of steam engines. Recently an interest in the two-phase injectors revived with new proposals of their application in thermal engineering, refrigeration and air conditioning. Low-pressure steam-water injectors may be applied as thermal driven liquid pump in absorption and steam ejection refrigeration systems. In this paper a close attention is paid to steam-water injectors in which superheated steam of relatively low pressure is the driving medium. …

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Investigations Of Heat And Momentum Transfer In Vapor-Liquid Isobutane Injector, Kamil Smierciew, Dariusz Butrymowicz, Tomasz Przybylinski Jan 2016

Investigations Of Heat And Momentum Transfer In Vapor-Liquid Isobutane Injector, Kamil Smierciew, Dariusz Butrymowicz, Tomasz Przybylinski

International Refrigeration and Air Conditioning Conference

Renewable energy sources may be applied to drive refrigeration and air-conditioning systems, e.g. solar radiation, geothermal resources, heat derived from biomass or waste heat rejected form various thermal processes. In this case absorption refrigeration systems and ejection systems may be used for cooling applications. In both these systems the crucial problem is the development of a suitable liquid pump.  Energy consumption to drive these systems is not a major problem here as in most cases amount of energy required to drive a mechanical pump is a contribution of at most a few percent of the overall energy balance of …

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Self-Learning Backlash Inverse Control Of Cooling Or Heating Coil Valves Having Backlash Hysteresis, Jie Cai, James E. Braun Jan 2016

Self-Learning Backlash Inverse Control Of Cooling Or Heating Coil Valves Having Backlash Hysteresis, Jie Cai, James E. Braun

International Refrigeration and Air Conditioning Conference

Valves are widely used in HVAC systems to regulate liquid flow rate, such as hot- and chilled-water valves utilized in cooling and heating coils. These valves are typically controlled with motorized actuators where significant backlash hysteresis might exist and the backlash magnitude mostly depends on the clearance of the manufactured gearbox. Due to the hysteresis effect, unsatisfactory tracking performance results when using a conventional PI controller. This paper proposes a self-learning backlash inverse control approach to mitigate the backlash effect with moderate modifications to a conventional PI control. In the proposed approach, a self-learning procedure is carried out at the …

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Biomechanics Of Retinal Venous Pulsations As Indicators Of Intracranial Pressure, Charles F. Babbs Jan 2016

Biomechanics Of Retinal Venous Pulsations As Indicators Of Intracranial Pressure, Charles F. Babbs

Weldon School of Biomedical Engineering Faculty Working Papers

The origin of retinal venous pulsations remains an open problem in physiology and medicine; so too, their exact relationship to intracranial pressure. This study takes a mathematical modeling approach to explore details of blood flow through the eye to reveal the mechanism of pulsations. The intravaginal, intraneural, and intraocular segments of the retinal arteries and veins are modeled as connected resistive-capacitive segments. The analysis incorporates two critical mechanical properties of these small blood vessels, not heretofore studied, which become significant under conditions of negative transmural pressures: (1) dramatically reduced compliance during flattening and (2) cross-sectional shape change as internal volume …

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Analysis Of Dynamic Stability Of Ejector Expansion Refrigeration System, Jianqiang Deng, Lixing Zheng, Fei Wang Jan 2016

Analysis Of Dynamic Stability Of Ejector Expansion Refrigeration System, Jianqiang Deng, Lixing Zheng, Fei Wang

International Refrigeration and Air Conditioning Conference

The stable operation of a system is restricted by the intrinsic characteristics, namely harmonious matching among and between structure parameters and operation parameters. In this paper, we put forward an analysis method of the dynamic stability of the refrigeration system based on the First Approximation Theory of Lyapunov Stability Theorem and the evaluation of stability margin. It is carried out by linearizing the governing equations and analyzing the eigenvalue form of coefficient matrix. And the minimum logarithmic decrement is calculated to represent the stability margin. Analyzing the stability of gas cooler confirms the consistency between the mathematical stability and the …

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Proportional-Integral Extremum Seeking For Optimizing Power Of Vapor Compression Systems, Daniel J Burns, Christopher R. Laughman, Martin Guay Jan 2016

Proportional-Integral Extremum Seeking For Optimizing Power Of Vapor Compression Systems, Daniel J Burns, Christopher R. Laughman, Martin Guay

International Refrigeration and Air Conditioning Conference

Conventionally, online methods for minimizing power consumption of vapor compression systems rely on the use of physical models. These model-based approaches attempt to describe the influence of commanded inputs, disturbances and setpoints on the thermodynamic behavior of the system and the resultant consumed electrical power. These models are then used online to predict the combination of inputs for a measured set of thermodynamic conditions that both meets the heat load and minimizes power consumption. However, these models of vapor compression systems must contain nonlinear terms of sufficient complexity in order to accurately describe the region near the optimum operating point(s), …

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Virtual Household Refrigerators At Steady-State And Transient Conditions. Numerical Model And Experimental Validation, Nicolas Ablanque, Carles Oliet, Joaquim Rigola, Carlos-David Pérez-Segarra Jan 2016

Virtual Household Refrigerators At Steady-State And Transient Conditions. Numerical Model And Experimental Validation, Nicolas Ablanque, Carles Oliet, Joaquim Rigola, Carlos-David Pérez-Segarra

International Refrigeration and Air Conditioning Conference

The aim of the present work is to present a comprehensive validation of a numerical model to simulate vapor compression refrigeration systems at steady state and transient conditions. The model simulates both the refrigeration cycle itself and the refrigerated compartments network, based on a modular approach where each element of the system is solved independently by means of appropriate models, while the whole system is solved iteratively based on the links established between the elements. The methodology implemented to achieve the transient simulation of the whole system combines a steady-state approach for the refrigerating cycle loop with a transient approach …

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Performance Evaluation Of Peripheral-Finned Tube Evaporators Under Frosting Conditions, Marco Timmermann, Jader Barbosa Jan 2016

Performance Evaluation Of Peripheral-Finned Tube Evaporators Under Frosting Conditions, Marco Timmermann, Jader Barbosa

International Refrigeration and Air Conditioning Conference

The peripheral finned-tube (PFT) is a novel air-side geometry for compact heat exchangers. Previous studies (Pussoli et al., Int. J. Heat Mass Transfer 55, 2835–2843, 2012) dealt with the evaluation of the thermal-hydraulic performance of the PFT geometry under dry conditions (i.e., no frost or condensate formation on the air side). The present study is focused on quantifying the thermal-hydraulic perfomance of the PFT geometry under frosting conditions. PFT evaporators were tested in a closed loop wind tunnel calorimeter to quantify the influence of the tube wall temperature, air velocity and air psychrometric properties (temperature and relative humidity) on the …

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Transient Modeling Of A Thermosiphon Based Air Conditioner With Compact Thermal Storage: Modeling And Validation, Rohit Dhumane, Yilin Du, Jiazhen Ling, Vikrant Aute, Reinhard Radermacher Jan 2016

Transient Modeling Of A Thermosiphon Based Air Conditioner With Compact Thermal Storage: Modeling And Validation, Rohit Dhumane, Yilin Du, Jiazhen Ling, Vikrant Aute, Reinhard Radermacher

International Refrigeration and Air Conditioning Conference

The Roving Comforter (RoCo) is an innovative personal thermal management technology currently being developed at the University of Maryland as part of Advanced Research Projects Agency – Energy (ARPA-e) project. Among several system configurations of RoCo, the paper focuses on a miniature battery-powered vapor compression cycle (VCC) system fitted on an autonomous robotic platform. The heat rejected from the condenser during its operation is stored in a compact phase change material (PCM) based heat storage device. The PCM can store only a limited amount of heat until it melts completely. The PCM heat exchanger needs to be designed so that …

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Numerical Simulation On Forced Convection Cooling Of Horizontal Ionic Wind With Multi-Electrodes, Rong Li, Yijian He, Guangming Chen, Fengshuo Wen Jan 2016

Numerical Simulation On Forced Convection Cooling Of Horizontal Ionic Wind With Multi-Electrodes, Rong Li, Yijian He, Guangming Chen, Fengshuo Wen

International Refrigeration and Air Conditioning Conference

Enhancement ofheat transfer plays an important role in the cooling of electronic or refrigeration systems, and its characteristics could strongly affect the stability and performance of such systems. To enhance heat transfer, air cooling of forced convection remains one of the main solutions. For example, conventional rotary-fan air cooling is still dominant in many areas. However, with the increasing of heat generation in these systems, the limitation of the conventional rotary-fan air cooling is become more obvious. So, demands in novel air cooling technology become necessary, e.g., silent and high efficient air cooling. Recently, ionic wind, which has no moving …

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Operation Analysis On Refrigeration System Combined With Heat Pipe, Haixia He, Wen Wang, Zhaogang Qi, Rui Zhuan, Qifan Gu Jan 2016

Operation Analysis On Refrigeration System Combined With Heat Pipe, Haixia He, Wen Wang, Zhaogang Qi, Rui Zhuan, Qifan Gu

International Refrigeration and Air Conditioning Conference

In data center, telco equipment station and some central control rooms, there are some cases with cooling requirement all the year, their temperatures are usually controlled strictly whenever in summer or in winter. Moreover, due to clearness and safety requirement, the chiller should provide cooling water all the time even the outside environment is very cold. There had been some considerations about provide cooling capacity in cold climate with free environmental air by various heat exchangers directly. Without operating chillers, annual energy consumption on temperature control could be decreased. This paper proposed a system combined a chiller with an air-cooled …

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Comparison Of Models For Calculation Of The Thermodynamic Properties Of Nh3-Co2-H2o Mixture, Vilborg Gudjonsdottir, Carlos Infante Ferreira Jan 2016

Comparison Of Models For Calculation Of The Thermodynamic Properties Of Nh3-Co2-H2o Mixture, Vilborg Gudjonsdottir, Carlos Infante Ferreira

International Refrigeration and Air Conditioning Conference

Couple of models have been developed to calculate thermodynamic properties of NH3-CO2-H2O systems. These models are typically an equation of state for the vapor phase and an activity coefficient model for the liquid phase (Que & Chen, 2011). The activity coefficient models can be divided into three groups based on previous studies, Pitzer model, electrolyte Non Random Two Liquid (e-NRTL) model and extended UNIQUAC model. Que & Chen (2011) deem the e-NRTL model the model the most suitable for process modelling and simulations since it requires only binary interaction parameters and makes use of mole fraction concentration scale consistently for …

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Heat Pumps Architecture Optimization For Enhanced Medium Temperature Geothermal Heat Use In District Heating, Matthildi Apostolou, Sahar Salame, Stéphanie Barrault, Assaad Zoughaib Jan 2016

Heat Pumps Architecture Optimization For Enhanced Medium Temperature Geothermal Heat Use In District Heating, Matthildi Apostolou, Sahar Salame, Stéphanie Barrault, Assaad Zoughaib

International Refrigeration and Air Conditioning Conference

Use of geothermal heat in distric heating allows increasing the share of renewable energy use. However, in many cases, this share is limited by the district heating required temperature and seasonnal load variation. Heat pumps permit upgrading geothermal heat by increasing further the temperature while pumping residual heat from the network return. Therefore not only they substitute boilers for upgrading the temperature but also increase the capacity of the geothermal heat source by reducing the return temperature. This paper presents a methodology for heat pumps architecture optimization enhancing the use of geothermal heat. The methodology allows considering two optimisation objectives: …

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Assessing Defrosting Performance On Hydrophilic, Hydrophobic, And Micro-Patterned Heat Transfer Surfaces, Nickolas C. Schmiesing, Andrew D. Sommers Jan 2016

Assessing Defrosting Performance On Hydrophilic, Hydrophobic, And Micro-Patterned Heat Transfer Surfaces, Nickolas C. Schmiesing, Andrew D. Sommers

International Refrigeration and Air Conditioning Conference

In this work, differences in drainage rates and defrosting effectiveness were explored for surfaces of differing wettability. Both patterned and non-patterned surfaces were explored. To date, six surfaces have been examined— an uncoated, untreated aluminum plate (Sample 1), an identical plate treated with a hydrophilic coating (Sample 2), a plate containing evenly-spaced micro-channels with no surface coating (Sample 3), a plate containing evenly-spaced micro-channels with a hydrophobic coating (Sample 4), and a surface containing a microstructural roughness gradient both with and without a hydrophobic surface coating (Samples 5 and 6). Cyclical tests containing frosting periods and defrosting periods were conducted …

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Modelling Of An Automotive Multi-Evaporator Air-Conditioning System, Thomas Gillet, Emmanuelle Andrès, Amin El-Bakkali, Gérard Olivier, Vincent Lemort, Romuald Rullière, Philippe Haberschill Jan 2016

Modelling Of An Automotive Multi-Evaporator Air-Conditioning System, Thomas Gillet, Emmanuelle Andrès, Amin El-Bakkali, Gérard Olivier, Vincent Lemort, Romuald Rullière, Philippe Haberschill

International Refrigeration and Air Conditioning Conference

With the arrival of plug-in hybrid electric vehicles (PHEV) and battery electric vehicles (BEV) with significant autonomy, battery cooling becomes a necessity in driving mode to ensure their durability and ability to charge rapidly. Â For these vehicles, the refrigerating system may be composed of two evaporators (for front and rear passengers) in order to afford cooled air in the cabin and a chiller or a built-in battery evaporator to cool down the traction battery. This kind of multi-evaporator air-conditioning system has a number of technological barriers that must be undone. They are related to the components sizing in a …

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Modelling And Simulation Of A R744 Based Air Conditioning Unit, Mihir Mouchum Hazarika, Maddali Ramgopal, Souvik Bhattacharyya Jan 2016

Modelling And Simulation Of A R744 Based Air Conditioning Unit, Mihir Mouchum Hazarika, Maddali Ramgopal, Souvik Bhattacharyya

International Refrigeration and Air Conditioning Conference

Studies show that the performance of transcritical R744 systems is highly sensitive to the high side pressure in the gas cooler. Hence use of appropriate strategy to control the high side pressure is essential to extract the best performance from these systems. In the present study, a R744 based air conditioning cycle with two expansion valves is considered for proper control of high side pressure and quality of refrigerant at evaporator exit. A system simulation model is developed for this cycle considering detailed model for each component. Both the gas cooler and evaporator considered here are crossflow heat exchangers with …

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An Improved Approach For Modeling Plate Heat Exchangers Based On Successive Substitution In Alternating Flow Directions, Radia Eldeeb, Vikrant Aute, Reinhard Radermacher Jan 2016

An Improved Approach For Modeling Plate Heat Exchangers Based On Successive Substitution In Alternating Flow Directions, Radia Eldeeb, Vikrant Aute, Reinhard Radermacher

International Refrigeration and Air Conditioning Conference

Finite volume modeling of plate heat exchangers is challenging in terms of computation time and robustness, especially in two-phase flow due to the coupling of pressure drop and heat transfer equations. Usually the entire heat exchanger is divided into segments and solved iteratively. Many thermophysical property calculations are required for each channel in each segment which is computationally expensive, especially with a high number of iterations. This led some models to employ pre-defined databases with many correction factors to overcome slow and unstable computation. In order to overcome this, an improved approach is developed for the analysis of plate heat …

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Viscosity Correlations For Refrigerants And Other Working Fluids From Residual Entropy Scaling, Ian Bell, Arno Laesecke Jan 2016

Viscosity Correlations For Refrigerants And Other Working Fluids From Residual Entropy Scaling, Ian Bell, Arno Laesecke

International Refrigeration and Air Conditioning Conference

We apply a modified scaling of viscosity with residual entropy in a manner analogous to that proposed by Rosenfeld (1977). We consider the viscosity-entropy scaling for a reference fluid (refrigerant R124 (1-chloro-1,2,2,2- tetrafluoroethane) ), and demonstrate that the viscosity for many other refrigerants scales with residual entropy in a similar manner. Finally, we use a corresponding-states formalism with one adjustable parameter to obtain the viscosity in a non-iterative fashion for a number of refrigerants. The viscosities of the studied fluids are represented within average absolute deviations of 10%. The evaluation of the liquid viscosity from this formulation is approximately 40 …

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