Showing papers on "Thermal expansion valve published in 2017"

Experimental assessment of R134a and its lower GWP alternative R513A

Abstract: Lower GWP refrigerants are essential to mitigate the impact of refrigeration systems on climate change. HFO/HFC mixtures are currently considered to replace HFCs in refrigeration and air conditioning systems. The aim of this paper is to present the main operating and performance differences between R513A (GWP of 573) and R134a (GWP of 1300), the most used refrigerants for medium evaporation temperature refrigeration systems and mobile air conditioners. To perform the experimental comparison, 36 tests are carried out with each refrigerant at evaporating temperatures between −15 and 12.5°C and condensing temperatures between 25 and 35°C. The conclusion of the experimental comparison is that R513A can substitute R134a with only a thermostatic expansion valve adjustment, achieving better performance and higher cooling capacity. The discharge temperature of R513A is always lower than that of R134a.

An analysis on the comparison of low-GWP refrigerants to alternatively use in mobile air-conditioning systems

Abstract: The results of an analysis are discussed in this paper considering R1234yf, R444A and R445A refrigerants having low Global Warming Potential (GWP) which can be used in the mobile air conditioning systems. The evaporation temperatures of −5 °C and +5 °C while condenser temperatures of 30 °C and 60 °C were taken for the evaluations of thermodynamic properties of the refrigerants. In the study, electrical power consumption of the system and COP values were calculated considering thermodynamic properties determined for the points in the cycle depending on the assumed system parameters. The system was considered to operate in a steady-state cycle. The pressure loss through evaporator and condenser, and heat transfer amounts through connecting tubes, expansion valve and compressor were neglected for the computations. The computations have pointed out that while cooling capacity of R444A and R445A were higher; their COP values were smaller compared to R1234yf because of their increased consumption of electricity. Although COP of R444A is smaller compared to R1234yf, it may be suggested that R444A can be utilized in air-conditioning systems of heavy vehicles such as busses, trucks, and trains due to its decreased flammability risk by mixture content.

Thermal and exergoeconomic analysis of a novel solar driven combined power and ejector refrigeration (CPER) system

Abstract: In the present study, a novel solar driven combined power and ejector refrigeration system (CPER) of 50 kW power capacity composed of an ORC (organic Rankine cycle) and an ejector refrigeration system is investigated. Solar driven CPER system is composed of two main cycles: collector cycle and refrigeration cycle. The collector cycle is made of a U-tube ETC and circulation pump and the ejector refrigeration cycle consists of generator, turbine, ejector, heat exchanger, condenser, evaporator, expansion valve, and pump. Thermodynamic performance of the proposed CPER system is evaluated and a thermo-economic analysis is conducted using the SPECO (specific exergy costing) method. A parametric study showed the effects of condenser temperature, evaporator temperature, generator pressure, turbine back pressure and turbine extraction ratio. The genetic algorithm optimization analysis is conducted which shows 25.5% improvement in thermal energy, 21.27% in exergy efficiency, and 7.76% reduction in the total cost of the CPER system. The results reveal that the performance of the CPER system is considerably improved at higher temperatures of generator and evaporator.

Experimental study of R450A drop-in performance in an R134a small capacity refrigeration unit

Abstract: The Kigali amendment to the Montreal Protocol has highlighted the hydrofluorocarbons (HFCs) phase out as a priority to reduce the future global mean temperature increase. R134a is the most abundant HFC in the atmosphere and therefore it must be substituted using environmentally benign alternatives. In the short term, blends of HFCs and hydrofluoroolefins can replace R134a. This paper experimentally evaluates R450A (GWP of 547), a non-flammable mixture of R1234ze(E) and R134a, in an R134a small capacity refrigeration system. The controlled experimental conditions cover evaporating temperatures from −15 to 12.5 °C and condensing temperature of 25, 30 and 35 °C (36 tests in total for each refrigerant). The experimental results showed that with only a thermostatic expansion valve adjustment the average R450A cooling capacity and COP are 9.9% and 2.9% lower than those measured using R134a. Besides, the observed compressor discharge temperature values of R450A are not greater than that of R134a.

Parametric analysis of domestic refrigerators using PCM heat exchanger

Abstract: In the present study, numerical simulation of refrigeration cycle incorporated with a PCM heat exchanger is carried out. To this end, the refrigeration cycle without PCM has been simulated and then, the performance coefficients of the refrigerator in either with and without PCM are evaluated. The PCM heat exchanger is located in the refrigeration cycle, at a location after the condenser and before the expansion valve. The utilised PCM is N-Octadecane with fusion temperature of 27.5 °C. The simulation of heat exchanger is based on computational fluid dynamics (CFD) in which the flow inside the pipe is considered one-dimensional in the axial extension and PCM surrounding it, is considered two dimensional. Numerical simulation is carried out using MATLAB software. Simulation results show that utilizing PCM in refrigeration cycle of a refrigerator causes an improvement in the convection procedure and results a 9.58% increase in performance coefficient of refrigerator.

Performance evaluation of ejector expansion combined cooling and power cycles

Abstract: This paper studies performance characteristics of a basic ejector expansion combined cooling and power cycle (EECCPC) as well as three modified ones. These modified cycles are EECCPC incorporating turbine bleeding, regenerative EECCP cycle, and EECCP cycle incorporating with both turbine bleeding and regeneration. The expansion valve has been replaced by a two-phase ejector-expander in the traditional CCP cycle to improve the first and second-law efficiencies. Furthermore, the exergy destruction for components of the systems as well as the whole systems has been calculated, leading to determination of the main source of irreversibility in different cycles. The results of the exergy analysis reveals that the generator has the major contribution role in the overall losses of the systems. The results also show that the EECCP cycle surpasses the TCCP cycle in terms of thermal and exergy efficiencies. As a matter of fact, the thermal and exergy efficiencies are improved by 6.02, and 5.44%, respectively, throughout this successive modification. At last, sensitivity analysis of different key parameters on performance of the cycles has been investigated. It is shown that one can obtain higher thermal efficiency by increasing of the generator and evaporator temperatures or decreasing of the condenser temperature.

Intelligentized multi-loop thermal management system of electric automobile

Abstract: The invention relates to an intelligentized multi-loop thermal management system of an electric automobile. The intelligentized multi-loop thermal management system comprises a power battery pack, a driving motor, a motor controller, a vehicle-mounted electric-charger, a DC/DC transducer, a battery radiator, a battery refrigerator, a motor radiator, a motor water pump, a motor oil pump, an expansion water tank, a PTC heater, a heat exchanger, a motor compressor, a condenser, a liquid storage drying kettle, an evaporator, a electric expansion valve and a heater core body. By interconnection between a direct-through valve, a three-direction valve and a four-way valve, a plurality of heat management controlling circuit is formed. Compare with the existing technology, the intelligentized multi-loop thermal management system forms a plurality of circuits which can meet different cooling or heating requirements. According to the power battery pack of the electric automobile, a electric-driving module and air-condition character and working status of passenger compartments, the circuits are selectively opened or closed, temperature balancing and high-efficiency run of the electric automobile are guaranteed, system energy is saved significantly, endurance mileage of the electric automobile is prolonged, and economy of automobiles is improved.

Evaluation of optimal subcooling in subcritical heat pump systems

Abstract: The performance of a transcritical cycle is highly dependent on the rejection pressure. The optimal rejection pressure depends mainly on the inlet and outlet temperatures at the heat sink (secondary fluid). For the subcritical cycles, recent studies have demonstrated that the performance of these systems depends significantly on the degree of subcooling and its optimal value varies depending on the application. This paper presents a general methodology to calculate the optimal subcooling depending on the boundary conditions. The refrigerants R290, R134a, R1234yf and R32 are analyzed. Exergy analysis is used in order to see the subcooling effect at condenser and expansion valve independently. The optimal subcooling strongly depends on the temperature lift at the secondary fluid, and it is found when two pinch points are given in the condenser, one at the condenser outlet and another one inside the condenser (at the refrigerant dew point).

Air conditioner and defrosting operation method therefor

Abstract: A hot gas bypass circuit that connects a discharge side of the compressor and a portion between the heat source side heat exchanger and the expansion valve, an on-off valve that opens and closes a channel of the hot gas bypass circuit, and a control device performing control to select one of hot gas bypass defrosting and reverse cycle defrosting according to a frosting amount on the heat source side heat exchanger and perform defrosting. The control device controls to open the on-off valve of the hot gas bypass circuit such that a part of a refrigerant discharged from the compressor is supplied to the heat source side heat exchanger via the hot gas bypass circuit and, the control device switches switch the four-way valve such that the refrigerant discharged from the compressor is supplied to the heat source side heat exchanger after passing through the four-way valve.

Air conditioner outlet air temperature control method and device

Abstract: The embodiment of the invention discloses an air conditioner outlet air temperature control method and a control device. The air conditioner outlet air temperature control method comprises the steps that a target outlet air temperature T0 is acquired; an indoor coil temperature T1 is detected; the difference between the indoor coil temperature T1 and the target air outlet temperature T0 is calculated; if T1-T0 is a positive number and the absolute value of the difference value is larger than a threshold value, the frequency of a regulation compressor is increased, and an expansion valve opening degree is reduced; and if T1-T0 is a negative number, the absolute value of the difference is larger than the threshold value, the frequency of the regulation compressor is reduced, and the expansion valve opening degree is increased. By means of the air conditioner outlet air temperature control method and device, the problem that as the temperature of air conditioner outlet air is too low or too high, the human body is stimulated easily can be solved so that the user experience can be improved.

Control method and device for air conditioner and air conditioner

Abstract: The invention discloses a control method and device for an air conditioner and the air conditioner. An indoor unit of the air conditioner includes a plurality of heat exchanging and air supplying units and a plurality of air outlets facing to different air supplying areas. The number of the air outlets is the same as that of the heat exchanging and air supplying units, and the air outlets correspond to the heat exchanging and air supplying units one by one. Each heat exchanging and air supplying unit comprises a heat exchanger, a fan, an expansion valve and an air guiding plate arranged on thecorresponding air outlet. The control method comprises the steps that the actual temperature of the indoor environment and the position of a user in the air supplying areas are detected; the temperature difference value between the actual temperature and the set temperature in the air supplying areas as well as the spacing between the user and the indoor unit are calculated and determined and arecompared with the preset temperature difference value interval and the spacing interval correspondingly; and the expansion valve opening degree of the corresponding heat exchanging and air supplyingunit is adjusted according to the comparison result of the temperature difference value, and the fan rotational speed and/or the angle of the air guiding plate of the corresponding heat exchanging andair supplying unit are adjusted according to the comparison result of the spacing. By means of the control method, parameters such as the air outlet temperature and the air supplying directions of the different air supplying areas of the air conditioner can be flexibly adjusted.

Power battery water-cooling unit system and intelligent temperature difference control method thereof

Abstract: The invention discloses a power battery water-cooling unit system and an intelligent temperature difference control method thereof. The power battery water-cooling unit system comprises a water cooling unit and a water cooling unit controller, wherein the water cooling unit comprises a compressor, a pressure switch, a condenser, a condensation fan, a liquid storing and drying tank, an expansion valve, a plate type exchanger, a PTC heater, a three-way valve, an inlet water temperature sensor, a power battery box, an outlet water temperature sensor, a water tank and an electronic water pump, wherein the compressor, the pressure switch, the condenser, the condensation fan, the liquid storing and drying tank, the expansion valve and the plate type exchanger are connected with each other in series. Through the power battery water-cooling unit system, the automation degree of the control of the power battery water-cooling unit is improved; the control system is capable of judging the difference between the battery average temperature and the outlet water temperature of the water cooling unit, adaptively adjusting operation rotation rate of the compressor, the electronic water pump and the condensation fan in real time through an intelligent control algorithm, indirectly controlling a battery to operate in the optimal temperature range and the optimal temperature difference range and predicting the battery temperature trend in advance through ampere-hour integral.

Improving Demand Response Potential of a Supermarket Refrigeration System: A Food Temperature Estimation Approach

Abstract: In a smart grid, the load shifting capabilities of demand-side devices such as supermarkets are of high interest. In supermarkets, this potential is represented by the ability to store energy in the thermal mass of refrigerated foodstuff. To harness the full load shifting potential, we propose a method for estimating food temperature based on measurements of evaporator expansion valve opening degree. This method requires no additional hardware or system modeling. We demonstrate the estimation method on a real supermarket display case, and the applicability of knowing food temperature is shown through tests on a full-scale supermarket refrigeration system made available by Danfoss A/S. The conducted application test shows that feedback based on food temperature can increase the demand flexibility during a step by approximately 60% the first 70 min and up to 100% over the first 150 min, thereby strengthening the demand response potential of supermarket refrigeration systems.

Demand flow for air cooled chillers

Abstract: In an air cooled chiller, a refrigerant pump and bypass valve connected in parallel feed refrigerant from the condenser to a receiver; the pump is activated in response to condenser pressure; and the bypass is used otherwise. The condenser fan is controlled based on power consumption by the air cooled chiller that varies with ambient conditions. An evaporator set point is reset to meet load conditions. An expansion valve for the evaporator is controlled based on chilled water temperature, Delta T, or information from an air handling unit. Feedback of valve setting or position, temperature of air, valve size, and/or importance of an air handling unit is used to control the flow of chilled water. A variable pressure curve or other relationship is used with the feedback to control flow of chilled water based on the load. Refrigerant temperature is controlled based on information from the air handling unit.