Showing papers on "Thermal expansion valve published in 2016"

Performance evaluation of a vapor injection refrigeration system using mixture refrigerant R290/R600a

Abstract: This work presents a performance evaluation of a vapor injection refrigeration system using a mixture refrigerant R290/R600a, through steady-state simulations used to accomplish a parametric analysis considering the influence of the refrigerant composition over the following parameters: COP; compressor power; refrigerant mass flow rate; refrigerant temperature glide; mass flow ratio between vapor and feed streams in the flash tank; liquid and vapor composition of flash tank outlet streams and compression ratio. Two cases, denominated A and B, considering different fixed temperatures at the refrigeration system were studied and their performances were compared with the one of a basic vapor compression cycle. A maximum COP was obtained for a mixture containing 40 wt% of R290. COP of vapor injection refrigeration cycle is 16–32% greater than the one of a vapor compression cycle, depending on the composition of the mixture refrigerant and pressure drop at the cycle upper-stage expansion valve.

Dynamic modeling study for a solar evaporator with expansion valve assembly of a transcritical CO2 heat pump

Abstract: Recently, there has been an increased interest in natural fluids from industry and scientific community who see it as one of the most promising alternatives to replace the traditional CFCs and HCFCs, especially in heat pumps for residential water heating. This work presents an investigation of the behavior of the solar evaporator and expansion valve assembly of a transcritical CO2 heat pump in transient and steady conditions. The dynamic behavior of systems using CO2 as a refrigerant is significantly influenced by the dynamics of the heat transfer mechanisms. The solar evaporator model is based on the equations of conservation of mass, momentum, and energy. The model validation is realized by comparing simulation results and experimental data. The model is a useful tool for analyzing the behavior in transient and steady conditions simulating various operating conditions of the heat pump including solar radiation, ambient temperature, wind speed and atmospheric conditions.

High efficiency air conditioning model based analysis for the automotive sector

Abstract: The air conditioning (A/C) system of the cabin is one of the most energy consuming auxiliaries in a vehicle and its optimization is a technological option suitable for achieving fuel consumption reduction in automotive sector. Hence, in this paper, the Authors present a mathematical model of the A/C system, starting from its single components: compressors, condenser, expansion valve and evaporator. The model considers off-design behavior of components, being this system often at partial load operating conditions. Therefore, considering fixed orifice as expansion device, performance of the whole system has been evaluated and an optimization of the components was derived. Their design influence has been assessed and, moreover, the opportunity to have an A/C condenser cooled by a liquid circuit in place of external air is discussed, considering the opportunity to integrate it into the main engine cooling system. The performances outlined using R1234yf showed a 22% reduction of compressor shaft power with respect to the air cooled condenser case and significant COP increase.

Air conditioner controlling method and device and air conditioner

Abstract: The invention discloses an air conditioner controlling method and device and an air conditioner. The controlling method comprises the steps of obtaining the set temperature, the set humidity, the indoor environment temperature and the indoor environment humidity of an indoor unit; calculating the temperature difference value between the set temperature and the environment temperature and the humidity difference value between the set humidity and the environment humidity, matching the temperature difference value and the humidity difference value with a preset temperature difference range and a preset humidity difference range correspondingly, and generating a matching result; and according to the matching result, controlling draught fans of one or more heat-exchanging and air-supplying units to operate at the high air gear, making draught fans of one or more other heat-exchanging and air-supplying units operate at the low air gear or the medium air gear, and increasing the opening degree of each expansion valve. By means of the air conditioner controlling method, when the air conditioner operates in the refrigeration mode and the dehumidification mode, the air-speed gears of difference air outlets and the opening degrees of the corresponding expansion valves are adjusted according to the temperature and humidity conditions of the indoor environment so that the air conditioner can meet the requirements of users for modes such as refrigeration and dehumidification.

Parametric study of fluid flow and heat transfer over louvered fins of air heat pump evaporator

Abstract: Two-dimensional numerical investigations of the fluid flow and heat transfer have been carried out for the laminar flow of the louvered fin-plate heat exchanger, designed to work as an air-source heat pump evaporator. The transferred heat and the pressure drop predicted by simulation have been compared with the corresponding experimental data taken from the literature. Two dimensional analyses of the louvered fins with varying geometry have been conducted. Simulations have been performed for different geometries with varying louver pitch, louver angle and different louver blade number. Constant inlet air temperature and varying velocity ranging from 2 to 8 m/s was assumed in the numerical experiments. The air-side performance is evaluated by calculating the temperature and the pressure drop ratio. Efficiency curves are obtained that can be used to select optimum louver geometry for the selected inlet parameters. A total of 363 different cases of various fin geometry for 7 different air velocities were investigated. The maximum heat transfer improvement interpreted in terms of the maximum efficiency has been obtained for the louver angle of 16 ◦ and the louver pitch of 1.35 mm. The presented results indicate that varying louver geometry might be a convenient way of enhancing performance of heat exchangers.

The influences of the operating characteristics of an Electronic Expansion Valve (EEV) on the operational stability of an EEV controlled direct expansion air conditioning system

Abstract: This paper reports on a study on the influences of the operating characteristics of a proportional–integral (PI) controlled Electronic Expansion Valve (EEV) on the operational stability of a direct expansion (DX) air conditioning (A/C) system. Using the classical control theory, EEV's PI settings and time constant of EEV's temperature sensor were analyzed. The theoretical analysis results using the classical control theory were further verified experimentally using an experimental DX A/C system. The study results showed that a larger proportional or integral gain would lead to a high chance for the EEV–evaporator control loop to become unstable, while slowing down the rate of degree of superheat (DS) signal transfer by increasing EEV's time constants may help mitigate system's operational instability. The results confirmed that the operating characteristics of an expansion valve in a refrigeration system could impact its operational stability.

Optimization and performance experiments of a MnCl2/CaCl2–NH3 two-stage solid sorption freezing system for a refrigerated truck

Abstract: Based on the earlier-established MnCl2/CaCl2–NH3 two-stage solid sorption freezing system for a refrigerated truck, a series of optimization designs are conducted in this prototype system. For sorption beds consisting of many unit tubes, the arrangement mode is changed to the staggered arrangement. Off-the-shelf heat exchangers from refrigeration industries are chosen as the evaporator and the condenser, and an expansion valve is also used. The total mass of the optimized system is reduced to approximately 150 kg. Firstly, different refrigerating temperatures ranging from −25 °C to 0 °C are investigated, and experimental results show the optimized system can easily satisfy requirement even for transporting frozen goods. The earlier-established system can only satisfy requirement for transporting fresh goods. Simultaneously, the cycle time can be reduced to 45 min. Through the optimization, both the refrigerating capacity and the total mass of the system can satisfy requirement of this refrigerated truck.

Loop heat pipe, method of manufacturing the same, and electronic device

Abstract: Disclosed loop heat pipe includes: an evaporator configured to vaporize a working fluid; a condenser configured to liquefy the working fluid; a liquid line connecting the evaporator and the condenser; a porous body provided in a columnar shape in the liquid line; and a vapor line connecting the evaporator and the condenser, and forming a loop together with the liquid line.

Refrigeration system with superheating, sub-cooling and refrigerant charge level control

Abstract: The refrigeration system includes a compressor, a condenser, an evaporator, one or both of a receiver drier unit and an accumulator unit fluidly connected by refrigerant lines to form a refrigerant circuit. The receiver drier unit includes a receiver drier and a first sensor, and the accumulator unit includes an accumulator and a second sensor. A controller is electrically connected to the first and second sensors and in some cases electrically connected to an electrical valve. The electrical valve is fluidly connected to a refrigerant reservoir. The controller determines the refrigerant charge level, and selectively controls the electrical valve to allow the refrigerant to flow from the refrigerant reservoir to the refrigerant circuit when the refrigerant charge level is below the predetermined refrigerant charge level.

Experimental research and optimization on the environmental friendly R1234yf refrigerant in automobile air conditioning system

Abstract: Currently, the refrigerant used in the automotive air conditioning system is R134a which has a high global warming potential (GWP) value, so people are eager to find a good replacement for it. According to recent studies, R1234yf is considered as one of the top candidates to replace R134a. In this article, the performances of R1234yf “drop-in” system and the optimization to the R1234yf system are experimentally studied and investigated. The expansion valve used for the R1234yf system is optimized by changing the charged fluid and adjusting the spring force. The results indicate that it can improve the performance of R1234yf system significantly through adjusting the thermostatic expansion valve. For the thermostatic expansion valves (TEVs) charged with R134a in thermal bulb, the system performance is optimal. Compared to the original expansion valve, for the R1234yf system applying the adjusted expansion valves, under different working conditions the cooling capacity increases by 11.3% averagely and the coefficient of performance (COP) increases by 8% averagely.

Method for controlling electronic expansion valves during multi-connected air conditioning unit heating

Abstract: The invention discloses a method for controlling an electronic expansion valves during multi-connected air conditioning unit heating. The method includes the following steps that firstly, the target air suction superheat degree Tr and the target supercooling degrees Tl of the expansion valves are set; secondly, whether the actual air suction superheat degree Ts-Tdef is equal to Tr or not is judged, if the actual air suction superheat degree Ts-Tdef is equal to Tr, the third step continues to be executed, and if the actual air suction superheat degree Ts-Tdef is not equal to Tr, the sixth step is executed; thirdly, whether the actual supercooling degrees tem-liq of the expansion valves are all in the Tl range or not is judged, if the actual supercooling degrees tem-liq of the expansion valves are all in the Tl range, the fourth step is executed, if the actual supercooling degrees tem-liq of the expansion valves are not all in the Tl range, the fifth step is executed, no adjustment is made, and the second step is executed; fifthly, when the actual supercooling degree tem-liq of a certain expansion valve is larger than the upper limit of T1, the valve is opened to a certain degree, when the actual supercooling degree tem-liq of a certain expansion valve is smaller than the lower limit of Tl, the valve is closed to a certain degree, and the second step is executed after adjustment is completed; sixthly, whether the actual supercooling degrees tem-liq of the expansion valves are all in the Tl range or not is judged, if the actual supercooling degrees tem-liq of the expansion valves are all in the Tl range, the seventh step continues to be executed, and if the actual supercooling degrees tem-liq of the expansion valves are not all in the Tl range, the eighth step is executed; seventhly, the step numbers of all the expansion valves are adjusted, and the second step is executed after adjustment is completed; and eighthly, when Ts-Tdef is larger than Tr, the expansion valves with tem-liq larger than the upper limit of Tl are opened to a certain degree, if Ts-Tdef is smaller than Tr, the expansion valves with tem-liq smaller than the lower limit of Tl are closed to a certain degree, and the second step is executed after adjustment. The method has the beneficial effects that a refrigerant is reasonably distributed, and a balance heating effect is achieved.

Integrated thermal energy module within an air-cooled evaporator design

Abstract: A transport refrigeration unit (TRU) includes a compressor. The TRU further includes a condenser disposed downstream of the compressor. The TRU further includes an expansion device disposed downstream of the condenser. The TRU farther includes a first flow control device disposed downstream of the condenser. The TRU farther includes a first evaporator disposed downstream of the expansion device and the first flow control device. The first evaporator is disposed upstream of a second flow control device. The second evaporator is disposed downstream of the first flow control device, the expansion device, and the second flow control device. The second evaporator includes a thermal accumulator. The second flow control device disposed upstream of the compressor.

Performance evaluation and optimal configuration analysis of a transcritical carbon dioxide/propylene cascade system with vortex tube expander in high-temperature cycle

Abstract: This paper presents a theoretical investigation on the thermal performance of a natural refrigerant-based cascade refrigeration-heat pump system used to produce both heating and cooling. A parametric evaluation is also presented for carbon dioxide-propylene working pair by varying parameters like evaporating, gas cooler exit temperature, and temperature difference in the cascade heat exchanger of the system. The topping cycle of the system is provided with a vortex tube instead of an expansion valve. The maximum increase in coefficient of performance of the present system is 5.9 % compared to that of the transcritical cascade cycle without vortex tube expander, in the assumed range of operating parameters. The model predicts performance parameters and operating conditions e.g., pressure, enthalpy, temperature, and entropy at different state points. The proposed transcritical model is optimized for overall coefficient of performance, intermediate temperature, and mass flow ratio with the help of multi-linear regression analysis. The influences of main parameters on the optimum design quantities are displayed in tables and figures. The cascade refrigeration-heat pump model with carbon dioxide/propylene as refrigerants is validated by comparing the coefficient of performance values with other reference cascade systems. This study could contribute to the further development and the optimal design of carbon dioxide-propylene cascade refrigeration systems.

Heat pump device

Abstract: PROBLEM TO BE SOLVED: To provide a heat pump device capable of implementing a switching operation between an ordinary refrigeration cycle and a defrosting cycle after surely discharging a liquid refrigerant in a heat exchanger.SOLUTION: A refrigeration circuit 30 is constituted to implement a liquid recovering operation for implementing a degassing operation while reducing an opening of an expansion valve 52 in comparison with the opening in an ordinary refrigeration cycle, before a switching operation, and includes detecting portions 71, 75, 76 detecting that a refrigerant flowing out from a heat exchanger 40, 53 applied as a condenser of the use-side heat exchanger 40 and the heat source-side heat exchanger 53 has an overheat state, during the liquid recovering operation. The refrigerant circuit 30 is constituted to terminate the liquid recovering operation and implement the switching operation, when the overheat state of the refrigerant is detected by the detecting portions 71, 75, 76 during the liquid recovering operation.SELECTED DRAWING: Figure 4

Comparative assessment on irreversible losses in heat pumps using R744/R32/R1234yf and R744/R32/R1234ze(E)

Abstract: This article presents an experimental assessment of coefficient of performance and irreversible loss in the heat pump cycle using hydro-fluoro-olefin base ternary mixtures: YF300 (R744/R32/R1234yf; 4/44/52 mass%), YF200 (R744/R32/R1234yf; 5/28/67 mass%), ZE300 (R744/R32/R1234ze(E); 4/43/53 mass%), and ZE200 (R744/R32/R1234ze(E); 9/29/62 mass%). The smaller volumetric capacity of YF200 and ZE200 increases the irreversible loss caused by the pressure drop with increasing heat load. ZE200, which has a temperature glide of approximately 22 K, increases the irreversible loss in the condenser, evaporator, and expansion valve. The experimental results indicate that YF300 and ZE300 could be potential alternatives to R410A and R32.

Vehicle air conditioner

Abstract: PROBLEM TO BE SOLVED: To decrease the number of portions to be sealed.SOLUTION: A seal member 92 including a seal through-hole 921 is disposed between a circumference of a partition through-hole 31 provided in a dash panel 3 and an air conditioner case 41, and pipe arrangement members (an expansion valve 5 and refrigerant pipes 61, 62) circulating refrigerant and a drainage pipe 42 formed in the air conditioner case 41 are passed through the common partition through-hole 31 and seal through-hole 921, thereby making it possible to decrease the number of portions to be sealed and eventually decrease the number of seal members.SELECTED DRAWING: Figure 3

Supercritical carbon dioxide power generation system

Abstract: A supercritical carbon dioxide power generation system is provided. The supercritical carbon dioxide power generation system may include a regenerator, a turbine, a heat recoverer, a condenser, a compressor an expansion valve, a flash tank, a heat exchanger, and an ejector, and may utilize waste heat of the supercritical carbon dioxide power generation system.

Vehicle air-conditioner system with battery heat management function

Abstract: A vehicle air-conditioner system with a battery heat management function comprises a compressor, a condenser, a first expansion valve and an evaporator. The compressor, the condenser, the first expansion valve and the evaporator are connected in the first flowing direction of a refrigerant to form an air-conditioner refrigeration circulation loop. The vehicle air-conditioner system further comprises a plate heat exchanger, a second expansion valve, an air-water heat exchanger, a fan, a water pump, an electric heater and a battery pack built-in heat exchanger. The fan is arranged on the air inlet side of the air-water heat exchanger. The compressor, the condenser, the second expansion valve and the plate heat exchanger are connected in the second flowing direction of the refrigerant to form a battery cooling low-temperature medium circulation loop. The battery pack built-in heat exchanger, the water pump, the plate heat exchanger, the air-water heat exchanger and the electric heater are connected in the water circulation direction to form a battery temperature adjusting medium circulation loop. According to the vehicle air-conditioner system, uniform management of the temperature inside a vehicle and the temperature of a battery is achieved, a battery pack is in the better temperature environment all the time during working, and it is ensured that the good refrigeration effect is achieved inside the vehicle.

Electrified hot management function's in pond vehicle air conditioning system

Abstract: Electrified hot management function's in pond vehicle air conditioning system is including compressor, condenser, first expansion valve, evaporimeter, according to the first mobile orientation of refrigerant, formation cooler air -conditioner circulation circuit is connected to compressor, condenser, first expansion valve, evaporimeter: still wrap rubbing board formula heat exchanger, second expansion valve, air - water heat exchanger, fan, water pump, electric heater and the built -in heat exchanger of battery package, the fan setting is in air - water heat exchanger's the side of admitting air, according to the second flow direction of refrigerant, compressor, condenser, second expansion valve, plate heat exchanger connect formation battery cooling low temperature media rotation return circuit, according to the recycling of water direction, the built -in heat exchanger of battery package, water pump, plate heat exchanger, air - water heat exchanger, electric heater connect and form the battery media rotation return circuit of adjusting the temperature. This vehicle air conditioning system has realized the unified management of in -car temperature and battery temperature, makes the battery package in the during operation is in preferred temperature environment all the time, and has guaranteed to have good refrigeration effect in the car.

Control of a thermal fluid heat exchanger with actuator dynamics

Abstract: In this paper we consider the problems of modeling and control of counter-flow heat exchangers when one includes actuator dynamics as part of the model. Most models of heat exchangers assume zero axial conduction which is known to cause numerical problems and impacts control design. This paper extends earlier work where we now include full-flux terms and allow for actuator dynamics. Motivation for this paper comes from problems of design and control of vapor compression systems where the vapor compression cycle includes two heat exchangers, a compressor and an expansion valve. The control inputs to the condenser (heat exchanger one) are outputs of the the compressor and inputs to the evaporator (heat exchanger two) are outputs to the expansion valve. Thus, the dynamics of the compressor, motors and expansion valve are important when designing controllers for the heat exchangers. We focus on a simple heat exchanger model which includes actuator dynamics and use this model to evaluate the impact of including full-flux terms on controller design. We establish that as the axial conduction terms approach zero, one obtains convergence to the hyperbolic model with no axial conduction. In the case where the flux terms are dropped and the flow is zero, the resulting (degenerate) ODE control system is no longer stabailizble. Numerical examples are provided to illustrate the theoretical results.