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Heat Transfer And Pressure Drop Of R1123/R32 Flow In Horizontal Microfin Tubes During Condensation And Evaporation, Chieko Kondou, Shigeru Koyama Jan 2018

Heat Transfer And Pressure Drop Of R1123/R32 Flow In Horizontal Microfin Tubes During Condensation And Evaporation, Chieko Kondou, Shigeru Koyama

International Refrigeration and Air Conditioning Conference

R1123 (tri fluoro ethylene; CF2 = CHF) has a GWP of approximately 1, a normal boiling point of -59 °C and a critical temperature of 59 °C, those are considered to be desirable for air condition systems. However, the concentration is limited below 60% because of the instability. Therefore, using this substance as a mixture coupled with R32 is attempted. In this study, heat transfer characteristics in a horizontal microfin tube are assessed for the new candidate of low GWP refrigerant mixture R1123 / R32 (40 / 60 mass%). Of the tested microfin tube, an outer diameter, an equivalent inner …

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The Effect Of Biphasic Refrigerant Flow On Refrigerator Noise, Carlos Eduardo Vendrami, Daniel Fretta De Souza, Hamann Eleomar, Tadeu Tonheiro Rodrigues, Edson Correa Miguel Jan 2018

The Effect Of Biphasic Refrigerant Flow On Refrigerator Noise, Carlos Eduardo Vendrami, Daniel Fretta De Souza, Hamann Eleomar, Tadeu Tonheiro Rodrigues, Edson Correa Miguel

International Refrigeration and Air Conditioning Conference

Nowadays, the sound level and the sound quality are two very important buying criteria for the final users of a household or light commercial appliance. In order to assure good noise levels, the choice of a compressor with low noise at a specific condition is not the only point necessary to care. It is important to evaluate the transient noise, specially the one that depends on the state and the phases of the refrigerant. The goal of this paper is to present two studies, the first one showing how a biphasic flow in the suction line, close to the compressor …

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Quality Measurement Of Two Phase Flow With Plug Flow, Mitsuhiro Fukuta, Shozo Miyata, Masaaki Motozawa, Shota Morishita, Naoya Makimoto Jan 2018

Quality Measurement Of Two Phase Flow With Plug Flow, Mitsuhiro Fukuta, Shozo Miyata, Masaaki Motozawa, Shota Morishita, Naoya Makimoto

International Refrigeration and Air Conditioning Conference

In order to control refrigeration cycles employing an injection system properly, it is important to detect quality of gas–liquid two-phase refrigerant in a two-phase region of the cycle. Although there are some techniques such as using a capacitance sensor or a X-ray beam scanning to measure a cross-sectional void fraction of the gas-liquid two-phase flow in a pipe, the measurement of the quality or flow rate of each phase is quite difficult since the liquid phase and gas phase of two-phase flow flowing in a pipe have different velocities in most cases. Meanwhile, the flow through a narrow tube becomes …

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Frost Growth Detection Using Capacitive Sensor, Yuchen Shen, Hongqing Jin, Xiaofei Wang Jan 2018

Frost Growth Detection Using Capacitive Sensor, Yuchen Shen, Hongqing Jin, Xiaofei Wang

International Refrigeration and Air Conditioning Conference

Frost buildup on surfaces could be an undesired situation in many applications. In refrigeration and heat pump system, typically, frost grows on the fin surface of the heat exchanger due to different environmental/operational conditions. On one hand, it can block the air flow and increase air-side pressure drop; on the other hand, can increase the thermal resistance and deteriorate heat transfer performance. As a result, frost buildup can significantly reduce the system’s COP. Therefore, most systems encountered frost buildup run the defrost cycle. The frost growth process is affected by many factors, such as environmental conditions (air humidity, temperature, flow …

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A 360 Degree View Of Selecting A Lubricant For My New Low Gwp Refrigerant, Joseph L. Nigro, Julie Majurin Jan 2018

A 360 Degree View Of Selecting A Lubricant For My New Low Gwp Refrigerant, Joseph L. Nigro, Julie Majurin

International Refrigeration and Air Conditioning Conference

The advent of environmentally friendly refrigerants and the global drive for higher efficiency is bringing change to our industry. A review of current HFC refrigerants and their lubricant choices over a range of evaporator temperatures will be summarized and compared to the numerous low GWP refrigerant replacements and associated lubricant considerations. The paper details a methodology for matching a refrigerant and a lubricant over a variety of low GWP refrigerant options. The current challenges in meeting miscibility, solubility, discharge temperature and working viscosity targets will be discussed and options presented. As the industry develops and implements both interim, lower GWP …

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Innovative Architecture To Valorize The Waste Heat Of A Passenger Car Through The Use Of A Rankine Cycle, Olivier Dumont, Davide Ziviani, James E. Braun, Eckhard A. Groll, Mouad Diny, Vincent Lemort Jan 2018

Innovative Architecture To Valorize The Waste Heat Of A Passenger Car Through The Use Of A Rankine Cycle, Olivier Dumont, Davide Ziviani, James E. Braun, Eckhard A. Groll, Mouad Diny, Vincent Lemort

International Refrigeration and Air Conditioning Conference

Passenger cars roughly represent 12% of the CO2 emissions in EU. Passenger car gasoline engines present large losses in thermal energy (roughly 60% in engine coolant and exhaust gases). This paper presents a new architecture of organic Rankine cycle using both sources of heat to decrease the emissions of the car with the cooling engine fluid as working fluid. It allows to decrease the cost, the complexity, environmental and safety issues. In this paper, the main losses of the system are taken into account: under and over-expansion of the expander, bypass flow, thermal power at the condenser limitation and exhaust …

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Surface Tension Measurement Of Low Gwp Refrigerant Mixture Hfo-1123/Hfc-32 And Hfo-1234ze(E)/Hfc-32, Chieko Kondou, Taisuke Matsuzono, Yukihiro Higashi Jan 2018

Surface Tension Measurement Of Low Gwp Refrigerant Mixture Hfo-1123/Hfc-32 And Hfo-1234ze(E)/Hfc-32, Chieko Kondou, Taisuke Matsuzono, Yukihiro Higashi

International Refrigeration and Air Conditioning Conference

HFOs (hydro-fluoro-olefins), HFO-1123 and HFO-1234ze(E) with GWP (global warming potential) of less than 1 attracted attention in a field of air conditioning and refrigeration engineering. However, the use of those HFO alone in such heat pump systems lucks adequate capacity or chemical stability. To compensate the shortcomings, mixtures coupled with R32 is considered to be one solution. This paper presents the surface tension measurement data of HFC-32, HFO-1123, and HFO-1234ze(E), and also their binary mixtures HFO-1123/HFC-32 and HFO-1234ze(E)/HFC-32 at various mass fractions. The capillary constant and surface tension of those are measured across temperature range from 267 K to 307 …

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Evaluation Of Binary And Ternary Refrigerant Blends As Replacements For R134a In An Air-Conditioning System, Ian Bell, Piotr Domanski, Greg Linteris, M. O. Mclinden Jan 2018

Evaluation Of Binary And Ternary Refrigerant Blends As Replacements For R134a In An Air-Conditioning System, Ian Bell, Piotr Domanski, Greg Linteris, M. O. Mclinden

International Refrigeration and Air Conditioning Conference

We investigated refrigerant blends as possible low-GWP (global warming potential) alternatives for R134a in an air-conditioning application. We carried out an extensive screening of the binary and ternary blends possible among a list of 10 pure refrigerants comprising three hydrofluoroolefins (HFOs), six hydrofluorocarbons (HFCs), and carbon dioxide. The screening was based on a simplified cycle model, but with the inclusion of pressure drops in the evaporator and condenser. The metrics for the evaluation were nonflammability, low-GWP, high COP (coefficient of performance), and a volumetric capacity similar to the R134a baseline system. While no mixture was ideal in all regards, we …

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Effect Of Flow Direction Of Heating Medium On Boiling Heat Transfer Characteristics In A Single-Channel Plate-Fin Heat Exchanger, Kazuaki Shikichi, Kenji Minoura, Hitoshi Asano Jan 2018

Effect Of Flow Direction Of Heating Medium On Boiling Heat Transfer Characteristics In A Single-Channel Plate-Fin Heat Exchanger, Kazuaki Shikichi, Kenji Minoura, Hitoshi Asano

International Refrigeration and Air Conditioning Conference

This study deals with evaporative heat transfer characteristics of vertically upward flows in single-channel plate-fin heat exchangers. R-134a was used as the refrigerant. The refrigerant channel was sandwiched by two water channels with the same channel shape. The refrigerant was heated by hot water from the both side. In this experiment, pressure of the working fluid was maintained at 0.665 MPa (saturation temperature is 25 °C)．Subcooled liquid with the subcooling of 5 and 10 K, or wet vapor with the quality of 0.1 was supplied to the evaporator. Two kinds of offset fin, Fin A and B, whose fin pitch …

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Non-Intrusive Performance Assessment Method For Heat Pumps: Experimental Validation And Robustness Evaluation Facing Faults, Derek Noël, Cédric Teuillieres, Philippe Riviere, Odile Cauret, Dominique Marchio Jan 2018

Non-Intrusive Performance Assessment Method For Heat Pumps: Experimental Validation And Robustness Evaluation Facing Faults, Derek Noël, Cédric Teuillieres, Philippe Riviere, Odile Cauret, Dominique Marchio

International Refrigeration and Air Conditioning Conference

Thanks to their high theoretical efficiency, residential heat pumps (HP) are a promising technology when attempting to reduce the energy consumption of heating in dwellings. Evaluation of their real performances on-field is thus crucial to promote their development and deployment. However, measuring accurately real heating capacity of air-to-air HP is not easy, since measuring air enthalpy and mass flow rate is challenging. A previously developed non-intrusive internal method based on the compressor energy balance has been improved. It can calculate the coefficient of performance (COP) of different HP types, including air-to-air, on field, thanks to real-time measurements, without interfering with …

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Accelerated Life Methods For Understanding Refrigerant Chemical Stability In Hvacr Systems, Steve Kujak, Elyse Marie Sorenson Jan 2018

Accelerated Life Methods For Understanding Refrigerant Chemical Stability In Hvacr Systems, Steve Kujak, Elyse Marie Sorenson

International Refrigeration and Air Conditioning Conference

Today’s air conditioning product and applications designers, as a result of climate change contribution concerns for high direct global warming potential (GWP) refrigerants, are being asked to consider lower GWP refrigerants which have potential for decreased chemical stability. Chlorofluorocarbons (CFCs) and hydrofluorocarbons (HCFCs) were developed after years of research and field experiences, while they presented some chemical stability concerns with materials, they still offered good product reliability. Hydrofluorocarbons (HFCs) that later replaced the CFCs and HCFCs were generally found to be more chemically stable with materials. In recent years, the HVACR industry has been actively investigating new lower GWP refrigerants, …

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Accelerating-Particle-Deposition Method For Quickly Evaluating Long-Term Performance Of Fin-And-Tube Heat Exchangers, Dawei Zhuang, Guoliang Ding, Yifei Yang, Feil Zhan, Yifeng Gao, Jun Shen, Ji Song Jan 2018

Accelerating-Particle-Deposition Method For Quickly Evaluating Long-Term Performance Of Fin-And-Tube Heat Exchangers, Dawei Zhuang, Guoliang Ding, Yifei Yang, Feil Zhan, Yifeng Gao, Jun Shen, Ji Song

International Refrigeration and Air Conditioning Conference

Fin-and-tube heat exchanger is the most commonly used heat exchanger type in air-conditioning systems. In the actual operation of air-conditioning systems, the dust particles involved in the air may partly deposit and form particulate fouling on fins and tubes when the dusty air flows through the heat exchangers. The deposited particles may gradually block the passageway of air flow and occupy the heat transfer area, which results in the continuous increase of air side thermal resistance and the significant deterioration of the heat transfer capacity of heat exchangers during the long-term operation. In order to quickly evaluate the long-term performance …

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Effect Of Saturation Temperature Change Due To Pressure Loss Of Refrigerants On Heat Transfer Capacity Of Heat Exchanger, Hyo In Lee, Tiandong Guo Jan 2018

Effect Of Saturation Temperature Change Due To Pressure Loss Of Refrigerants On Heat Transfer Capacity Of Heat Exchanger, Hyo In Lee, Tiandong Guo

International Refrigeration and Air Conditioning Conference

Heat exchanger is an essential component in the HVAC&R applications. The heat exchanger development methods are divided into simulation and experiment. Simulation is often used by researchers because it can save a lot of time and money over experimental method. However, it is difficult to model all physical phenomena in simulation. Some phenomena are simulated with ideal assumptions based on experience. To analyze an ideal heat exchanger without pressure loss of the refrigerant, the saturation temperature of the heat exchanger is assumed to be constant. Whereas, saturated temperature drop occurs due to the pressure loss of the refrigerant in a …

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Effects Of Airflow Direction, Air Velocity Profile, And Condensation Pressure On The Performance Of Air-Cooled Condensers, William A. Davies, Predrag S. Hrnjak Jan 2018

Effects Of Airflow Direction, Air Velocity Profile, And Condensation Pressure On The Performance Of Air-Cooled Condensers, William A. Davies, Predrag S. Hrnjak

International Refrigeration and Air Conditioning Conference

Experimental results for steam condensation in large, flattened-tube air-cooled condensers are presented. Capacity, void fraction, and steam-side pressure drop and heat transfer coefficient are measured, and visualization is performed simultaneously. Capacity and pressure drop results are discussed here. The condenser tube has an elongated-slot cross-section, with inner dimensions of 214 x 16 mm. The tube is 10.7 m long. Steam mass flux ranges from 6-10 kgm-2s-1, average air-side velocities were 1.8 and 2.2 m s-1, and steam condensation pressure ranges from 90-105 kPa. All tests are performed with a horizontal tube and co-current vapor and condensate flow. Three different profiles …

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Flow Regime Map For Condensation From Superheated Vapor, Jiange Xiao, Predrag S. Hrnjak Jan 2018

Flow Regime Map For Condensation From Superheated Vapor, Jiange Xiao, Predrag S. Hrnjak

International Refrigeration and Air Conditioning Conference

An update on the flow regime map for condensation inside horizontal smooth round tubes accounting for the non-equilibrium existed in a vapor compression system is presented. Current flow regime maps are made in the range of bulk quality between 1 and 0. However, the temperature gradient required by condensation means that the thermal equilibrium assumed in a thermodynamic point of view does not exist in a real condenser, especially at the entrance of a condenser in vapor compression systems. By focusing on the development of the liquid film when the superheated vapor is condensed on the tube wall whose temperature …

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Transient Distribution Of Refrigerant And Oil In A Residential Heat Pump Water Heater System, Wenzhe Li, Predrag S. Hrnjak Jan 2018

Transient Distribution Of Refrigerant And Oil In A Residential Heat Pump Water Heater System, Wenzhe Li, Predrag S. Hrnjak

International Refrigeration and Air Conditioning Conference

This paper presents an experimental investigation of transient refrigerant and oil migration in a residential heat pump water heater (HPWH) system. In the experiments, R134a is paired with POE 22 oil. The Quick Closing Valve Technique (QCVT) is employed to localize the refrigerant and oil into each section of the system. The Remove and Weigh Technique (RWT) is then applied to measure the trapped refrigerant mass in the sections, with an uncertainty about 0.17% of the total refrigerant charge. The retained oil mass in each section, except for the compressor, is determined by the Mix and Sample Technique (MST), of …

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Experimental Characterization Of Flow Field Around Heat Exchanger Cells In A Residential Gas Furnace, Puyuan Wu, Weixiao Shang, Jun Chen Jan 2018

Experimental Characterization Of Flow Field Around Heat Exchanger Cells In A Residential Gas Furnace, Puyuan Wu, Weixiao Shang, Jun Chen

International Refrigeration and Air Conditioning Conference

DOE recently proposed to significantly increase the minimum furnace efficiency standards. This stringent requirement presents a major challenge to manufacturers for designing the next-generation product, which heavily relies on CFD-based design tool. In this study, Particle Image Velocimetry (PIV) is applied to measure the flow field around heat exchanger cells in a general model of a residential gas furnace to provide benchmark validation of CFD validations and to inspire new designs that must abide by the new regulations. The gas furnace, combined with inlet and outlet duct and a large exhaust chamber, can simulate a set of realistic operational conditions …

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Dynamics Of Frost Growth On Vertical Superhydrophobic Surfaces, Kalyan Satyadeep Boyina, Kazi Fazle Rabbi, Wei Su, Anand Thamban, Nenad Miljkovic, Xiaofei Wang Jan 2018

Dynamics Of Frost Growth On Vertical Superhydrophobic Surfaces, Kalyan Satyadeep Boyina, Kazi Fazle Rabbi, Wei Su, Anand Thamban, Nenad Miljkovic, Xiaofei Wang

International Refrigeration and Air Conditioning Conference

Superhydrophobic surfaces, which promote the efficient removal of condensing droplets prior to supercooling and freezing through coalescence induced jumping, have been shown to delay frosting significantly. The performance of fin and tube heat exchangers used in refrigeration and heat pump applications has the potential for improvement when coated with suitably designed superhydrophobic coatings. Currently, state-of-the-art (SOA) fins and their spacing are designed carefully to optimize pressure drop and heat transfer. The interaction amongst condensate droplets on adjacent fins can enhance the rate of condensate removal, and contribute to frost formation delay. Therefore, understanding the dynamics of droplet jumping within the …

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Pressure Drop Of Condensation From Superheated Vapor Inside Horizontal Smooth Round Tubes, Jiange Xiao, Predrag S. Hrnjak Jan 2018

Pressure Drop Of Condensation From Superheated Vapor Inside Horizontal Smooth Round Tubes, Jiange Xiao, Predrag S. Hrnjak

International Refrigeration and Air Conditioning Conference

Pressure drop of R134a, R32 and R1233zd(E) is measured and reported in diabatic conditions during condensation from superheated vapor inside horizontal smooth round tubes. The test conditions include mass fluxes from 100 to 400 kg m-2 s-1, heat fluxes from 5 to 15 kW m-2 and tube diameters of 4 and 6 mm at saturation temperatures of 30 oC. Compared to a conventional pressure drop model constructed under the assumption of thermal equilibrium, the experimental data clearly shows that the onset and end of condensation, instead of being fixed at bulk quality 1 and 0, actually is changing according to …

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Experimental Analysis Of Natural Refrigerant Blends For Household Application, Ramona Nosbers, Franziska Schmieder, Ullrich Hesse Jan 2018

Experimental Analysis Of Natural Refrigerant Blends For Household Application, Ramona Nosbers, Franziska Schmieder, Ullrich Hesse

International Refrigeration and Air Conditioning Conference

Hydrofluorocarbon (HFCs), due to their high global warming impact, are not considered a desirable solution for future household application. In accordance to the Kigali Amendment to the Montreal Protocol, numerous countries committed the significant face- down of the production and consumption of HFCs over the next two to three decades. Natural refrigerants as well as their blends are considered viable alternatives due to their low global warming potentials. Additionally, the use of non-azeotropic refrigerant blends can positively influence the cycle performance of refrigerators and heat pump tumble dryers. Moreover, the knowledge of the behaviour of the oil-refrigerant-mixture is a necessity …

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Flow Visualization Of Two-Phase R-245fa At Low Mass Flux In A Plate Heat Exchanger Near The Micro-Macroscale Transition, Hyun Jin Kim, Leon Liebenberg, Anthony M. Jacobi Jan 2018

Flow Visualization Of Two-Phase R-245fa At Low Mass Flux In A Plate Heat Exchanger Near The Micro-Macroscale Transition, Hyun Jin Kim, Leon Liebenberg, Anthony M. Jacobi

International Refrigeration and Air Conditioning Conference

Two-phase R-245fa flow in a plate heat exchanger is experimentally investigated to understand the unique flow regimes found during operation at low refrigerant mass flux. A transparent plate heat exchanger replica with 3.4 mm hydraulic diameter is 3D-printed for flow visualization using high-speed videography. Observed flow regimes support that the thermofluidic characteristics peculiar to plate heat exchanger (PHE) operation are due to the macro-microscale transitional two-phase flow from the coexistence of fluid inertial force and surface tension effects, corresponding to the operation conditions. Maximum stable bubble diameter is bigger at low mass flux than at high mass flux, and the …

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Effect Of Helix Angle On Flow Of R410a During Evaporation Inside Horizontal Round Tubes Based On Visualization In Diabatic Condition, Cheng-Min Yang, Predrag S. Hrnjak Jan 2018

Effect Of Helix Angle On Flow Of R410a During Evaporation Inside Horizontal Round Tubes Based On Visualization In Diabatic Condition, Cheng-Min Yang, Predrag S. Hrnjak

International Refrigeration and Air Conditioning Conference

This paper presents the effect of the helix angle on flow boiling in micro-finned tubes supported by a novel visualization in diabatic conditions. Such visualization helps better understanding of the mechanism of boiling and heat transfer enhancement. In most of the literature, the flow regime of flow boiling in the micro-finned evaporator tube is visualized by the sight glass without internal fin geometry and at the exit of the test section. In order to better understand effect of micro-fins on flow regime in the visualization test section, transparent micro-finned tubes with different helix angles placed in outer glass tube with …

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High-Temperature Heat Pump For Wellness Applications Using Co2 As A Refrigerant, Christian Kevin Seitz, Anne Liebold, Hendrik Schönfeld, Robert Weber, Stefan Bertsch Jan 2018

High-Temperature Heat Pump For Wellness Applications Using Co2 As A Refrigerant, Christian Kevin Seitz, Anne Liebold, Hendrik Schönfeld, Robert Weber, Stefan Bertsch

International Refrigeration and Air Conditioning Conference

Building technology recently has been affected by great innovations to reduce energy demand and to enable self-sufficient operation. To test innovations and prove practicality, EMPA has built a research building called NEST, where different demonstration projects from the building industry can be integrated and scientifically monitored. Furthermore, the sector of wellness applications shows significant potential for improving energy efficiency. Usually, spa facilities such as saunas and steam baths are based on direct electric or fossil heating which is extremely energy intensive and results in high operating costs. In order to establish a more energy efficient technology to provide heat to …

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The Effect Of Refrigeration Lubricant Properties On Nucleate Pool Boiling Heat Transfer Performance, Jung-Tsung Hung, Yu-Kai Chen, Hou-Kuang Shih, Shou-Ren Sheng, Chi-Chuan Wang Jan 2018

The Effect Of Refrigeration Lubricant Properties On Nucleate Pool Boiling Heat Transfer Performance, Jung-Tsung Hung, Yu-Kai Chen, Hou-Kuang Shih, Shou-Ren Sheng, Chi-Chuan Wang

International Refrigeration and Air Conditioning Conference

Refrigeration lubricant plays a key role in lubricating and sealing during vapor compression processes. However, it may migrate to the evaporator to influence the heat transfer characteristics, either enhancement or degradation. The aim of this study is to fundamentally understand the effect of lubricant properties and bubble parameters on heat transfer performance. To clarify parameters affecting the heat transfer coefficient, several experiments were conducted on a horizontal flat surface, and pool-boiling phenomenon was recording by high-speed camera. Comparisons of heat transfer measurements for different refrigerant/lubricant mixtures were made, including two different refrigerants (R-134a & R-1234ze) and eight POE lubricants with …

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Performance Evaluation Of Co2 Ejector System With Parallel Compressor For Supermarket Application, Simarpreet Singh, Krzysztof Banasiak, Armin Hafner, Maiya M P, Petter Nekså Jan 2018

Performance Evaluation Of Co2 Ejector System With Parallel Compressor For Supermarket Application, Simarpreet Singh, Krzysztof Banasiak, Armin Hafner, Maiya M P, Petter Nekså

International Refrigeration and Air Conditioning Conference

Evolution in modifications for CO2 system configuration came across from the last two decades has proven to hold the potential in order to improve the overall performance of the CO2 cooling system for various applications. However, performance of the CO2 system at high ambient context is not promising and comparable with popular conventional refrigerants. Due to its unique properties, the CO2 system possesses substantial losses at high ambient temperature due to the throttling process. System configuration with parallel compressor is proven as the most popular and efficient configuration for high ambient temperature (up to 46 °C). In this study performance …

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Experimental Evaluation Of Co2 Ejector Cooling System For Supermarkets At Tropical Zones, Simarpreet Singh, Armin Hafner, Krzysztof Banasiak, Maiya M P Jan 2018

Experimental Evaluation Of Co2 Ejector Cooling System For Supermarkets At Tropical Zones, Simarpreet Singh, Armin Hafner, Krzysztof Banasiak, Maiya M P

International Refrigeration and Air Conditioning Conference

Cooling system for supermarkets, now-a-days in developing countries like India, mainly use man-made synthetic refrigerants/mixtures such as R134a, R404A and R410A (HFCs). These fluorinated refrigerants possess outrageous impact on the environment/ambient due of their high GWP and ODP. The EU F-gas regulation is formulated recently and came into force in 2014 in order to restrict the use of synthetic refrigerants for various HVAC applications. Under this regulation, it is also illegal to vent any such synthetic refrigerants to the atmosphere during the system servicing or end-of-life decommissioning. Sudden phase down of HFCs forced the present scenario to identify a potential …

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Design And Investigation Of A Transcritical R744 Refrigerated Container For Military Applications, Neal Lawrence, Stefan Elbel, Predrag S. Hrnjak Jan 2018

Design And Investigation Of A Transcritical R744 Refrigerated Container For Military Applications, Neal Lawrence, Stefan Elbel, Predrag S. Hrnjak

International Refrigeration and Air Conditioning Conference

This paper describes the design and performance evaluation of a transcritical R744 (CO2) multi-temperature, mobile refrigerated container system. The efficient and widespread use of R744 in both large-scale supermarket refrigeration systems and small-scale glass-door merchandisers has been shown through numerous studies and field demonstrations in recent years, indicating the suitability of this refrigerant to almost any refrigeration application. However, the extreme operating conditions of this refrigeration application intended for use in ambient temperatures up to 57°C while still maintaining a frozen temperature of -20°C make using R744 as a refrigerant a unique challenge here. The targeted use of the refrigerated …

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Model-Based Air Flow Path Optimization For Heat Pump Clothes Dryer, Bo Shen, Kyle Gluesenkamp, Philip R. Boudreaus, Viral K. Patel Jan 2018

Model-Based Air Flow Path Optimization For Heat Pump Clothes Dryer, Bo Shen, Kyle Gluesenkamp, Philip R. Boudreaus, Viral K. Patel

International Refrigeration and Air Conditioning Conference

A heat pump clothes dryer (HPCD) is an innovative appliance that uses a vapor compression system to dry clothes. Air circulates in a closed loop through the drum, so no vent is required. The condenser heats air to evaporate moisture out of the clothes, and the evaporator condenses water out of the air stream. As a result, the HPCD can achieve 50% energy savings compared to a conventional electric resistance dryer. We developed a physics-based, quasi-steady-state HPCD system model with detailed heat exchanger and compressor models. The system model is able to simulate the inherently transient HPCD drying process, to …

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Development And Validation Of A Mechanistic Vapor-Compression Cycle Model, Ammar M. Bahman, Davide Ziviani, Eckhard A. Groll Jan 2018

Development And Validation Of A Mechanistic Vapor-Compression Cycle Model, Ammar M. Bahman, Davide Ziviani, Eckhard A. Groll

International Refrigeration and Air Conditioning Conference

Detailed models are crucial tools for engineers in designing and optimizing systems. In particular, mechanistic modeling of vapor compression systems for accurate performance predictions at both full- and part-load conditions have been improved significantly in the past decades. Yet, fully deterministic models present still challenges in estimating charge inventory in order to optimize the performance. In this work, a generalized framework for simulating vapor compression cycles (VCC) has been develvoped with emphasis on a charge-sensitive model. In order to illustrate the capabilities of the tool, a direct–expansion (DX) cycle has been considered. In the cycle model, the compressor was mapped …

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Review Of Shape And Topology Optimization For Design Of Air-To-Refrigerant Heat Exchangers, James Tancabel, Vikrant Chandramohan Aute, Reinhard Radermacher Jan 2018

Review Of Shape And Topology Optimization For Design Of Air-To-Refrigerant Heat Exchangers, James Tancabel, Vikrant Chandramohan Aute, Reinhard Radermacher

International Refrigeration and Air Conditioning Conference

Air-to-refrigerant heat exchangers (HXs) have been the topic of exhaustive research as they are fundamental components of HVAC&R systems. It has been well-established that the large airside thermal resistance dominates the HX thermal resistance, and thus significant research efforts have focused on improving the air-side performance of these heat exchangers. As HXs continue to become more compact, thermal resistance reduction is typically realized through the utilization of extended secondary heat transfer surfaces such as fins. However, past research has shown that the thermal-hydraulic trade-offs provided by fins are often not attractive enough to warrant their use, especially for small diameter …

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