Thermostatic Expansion Valve Research Articles

Sanford Klein and Gregory Nellis: Thermodynamics

This book provides a real excellence in a pool of knowledge and intelligence for graduate; post graduated and doctorate level courses in thermodynamics with the basic principles, concepts/fundamentals, tools, and practical examples in the field of engineering and technology. The selection of all the 16 chapters is structured to provide a good introduction to the subject and its importance to its reader. The concepts and techniques used in all major concerns of thermodynamics such as; entropy, enthalpy, power cycles, refrigeration cycles, heat pumps, combustion process, psychometric, and fluid flows are explained well and in an understandable manner. A total of total 82 examples, 415 colored figures, and 54 tables are given in the book (including the figures, and tables of solved examples and appendixes). Figures with their subsections say ‘‘a’’, ‘‘b’’, ‘‘c’’, are counted as one figure. Apart this, a computer programme ‘‘Engineering Equation Solver— (EES)’’, is introduced as a platform for numerical solution of the problems in an approachable manner (as well as eliminating the mathematical complexity involved to solve thermodynamics problems). Besides this, EES has been featured to check the dimensional and unit consistency of the equations. All the illustrations, tables, appendixes, as well as references are provided for better understanding the terms, their meanings, and source of referred literature to its reader. Chapters 1 and 2 deal with fundamentals of ‘‘Thermodynamics,’’ such as: laws of thermodynamics, thermodynamic states, and properties of various fluids used for heat transfer (heating and cooling). Fluid property data of the type, represented by smart figures, and based on the available data (mainly for liquid water and for steam) or sets of data (provided in the Appendix). A basic introduction of EES is given by solving the different problems of heat transfer and energy balances for thermal systems. Operations such as; vacuum by condensation, superheated vapor, thermostatic expansion valve, thermal driven compressor, and fire extinguishing system are explained well in details. Chapter 3 serves a practical theory and relative information on heat transfer and thermal behavior of the open and closed systems under various loads or ideal conditions. The energy balance equations are discussed to determine the thermal behavior of the systems in this section. It has also been stated and discussed that energy is a conserved quantity (in the terms of function of various works) in this chapter. Chapters 4 and 5 have been designed purposely to make comprehensible the concepts of first and second law of thermodynamics and their applications. A general methodology for solving thermodynamics problems that can be summarized as;

Experimental evaluation of a geothermal heat pump for space heating and domestic hot water simultaneous production

This paper deals with the experimental performance evaluation of a geothermal heat pump (GHP) intended to produce space heating (SH) and domestic hot water (DHW) simultaneously. The GHP uses R407C as refrigerant and its main components are a scroll compressor, a thermostatic expansion valve, a plate heat exchanger as evaporator and a condensing section composed of two plate heat exchangers connected in series, operating as a desuperheater and a condenser. In the condensing section, water is heated at two temperature levels for the SH and DHW systems. The experimental results realize the high influence of the water temperature at the condensing section inlet on the GHP behaviour. The COP and the heating capacity decrease 48.7% and 5.6% by increasing the water temperature at the condenser inlet from 20 to 50 °C, respectively. The percentage of water flow rate diverted to the desuperheater for DHW production depends on the water temperature and flow rate at the condensing section inlet. However, the heat transfer rate at the desuperheater remains nearly constant regardless of the water flow rate at the condensing section inlet and the water flow rate driven through the desuperheater. The experimental results also show that the water temperature inlet at the condensing section determines the proportion of the heat transfer rate delivered at the desuperheater for DHW production and at the condenser for SH.

LOW CHARGE TRANSPORT REFRIGERATOR (II). THEORETICAL AND EXPERIMENTAL INVESTIGATION

Considering the environmental challenges the refrigerant charge minimization is one of the most important targets for refrigerating and air conditioning applications. This paper presents a charge minimization study of transport refrigerator with eutectic plates. It was found that in traditional system significant charge increase in evaporator during the initial stage of pull-down was caused by interaction of thermostatic expansion valve and outlet pressure downstream regulator. For the baseline system (A) the charge increase was ~1 kg, i.e. 25% of total charge. This charge increase may be minimized through implementation of different control systems. Other important factors are the volumes of receiver, heat exchangers and liquid line. Two low-charge refrigerators with different control systems were developed and tested. The charge decrease was 40-50% comparing to baseline systems.DOI: http://dx.doi.org/10.5755/j01.mech.18.1.1290

Experimental analysis of a direct expansion solar assisted heat pump with integral storage tank for domestic water heating under zero solar radiation conditions

This paper deals with the experimental evaluation of the performance of a direct expansion solar assisted heat pump water heating (DX-SAHPWH) system working under zero solar radiation conditions at static heating operation mode of the storage tank. The DX-SAHPWH system includes two bare solar collectors as evaporator, a R134a rotary-type hermetic compressor, a thermostatic expansion valve and a helical coil condenser immersed in a 300L water storage tank. The zero solar radiation and stable ambient air temperature working conditions were established by placing the solar collectors into a climate chamber. The analysis is based on experimental data taken from the DX-SAHPWH provided by the manufacturer and equipped with an appropriate data acquisition system.In the paper, the experimental facility, the data acquisition system and the experimental methodology are described. Performance parameters to evaluate the energy efficiency, such as COP and equivalent seasonal performance factors (SPFe) for the heating period, and the water thermal stratification in the storage tank are defined and obtained from the experimental data. Results from the experimental analysis under transient operating working conditions of the DX-SAHPWH system and its main components are shown and discussed. Lastly, the Huang and Lee DX-SAHPWH performance evaluation method was applied resulting in a characteristic COP of 3.23 for the DX-SAHPWH system evaluated under zero solar radiation condition.

Performance Evaluation of an Automobile Air Conditioning System Using R134a

In this paper, a detailed energy and exergy analysis have been dealt with on experimental AAC (Automobile Air Conditioning) system with R134a as working refrigerant. For this aim, an experimental AAC system consisting of a laminated type evaporator, swash plate type compressor, a parallel flow type condenser, TXV(thermostatic expansion valve) and a receiver drier. The performance analysis of separate components of AAC system has been carried out under various compressor speeds and thermal loads. AAC system equipped with increasing compressor speed by three-phase electric motor controlled by frequency converter. Various thermal loads in the range of 1500 and 2850 W were applied to the system by means of electric heaters. The experiments were conducted at the condensing temperatures of 50-60 oC for each thermal load, and at the compressor speeds of 600, 800, 1000, 1200, 1400 rpm for each thermal load-condensing temperature combination. The refrigerant and air temperatures, refrigerant pressures, compressor speed, air velocity passing through the evaporator and thermal load were measured. Effects on system performance of such operational parameters as compressor speed, return air in the evaporator and condensing air temperatures have been experimentally evaluated and by means of energy and exergy analysis.

THERMOSTATIC EXPANSION VALVE HAVING A RESTRICTED FLOW PASSAGE FOR NOISE ATTENUATION

A thermostatic expansion valve includes a valve body having an evaporator inlet port, an evaporator outlet port, a suction line port, and a liquid line port. A sensor chamber formed within the valve body is disposed between the evaporator outlet port and the suction line port. A valve is disposed within the valve body controls a flow of refrigerant from the liquid line port to the evaporator inlet port. A diaphragm separates a charge chamber and a pressure chamber where a pressure differential between a charge chamber and a pressure chamber controls the positioning of the valve. A restriction flow passage located to provide fluid communication between the sensor chamber and the pressure chamber is configured to limit a flow rate from the pressure chamber to sensor chamber, thereby slowing the opening of the valve resulting in a reduction of noise generated following an initial startup of a compressor.

Experimental analysis of an adsorption refrigerator with mass and heat-pipe heat recovery process

A heat pipe type adsorption refrigerator system is proposed and investigated, which can be powered by solar energy or waste heat of engine. The study assesses the performance of compound adsorbent (CaCl 2 and activated carbon)–ammonia adsorption refrigeration cycle with different orifice sets and different mass and heat recovery processes by experimental prototype machine. Specific cooling power (SCP) and coefficient of performance (COP) were calculated with experimental data to analyze the influences of operating condition. The results show that the jaw opening of the hand needle nozzle can influence the adsorption performance obviously and the thermostatic expansion valve (TEV) is effective in the intermediate cycle time in the adsorption refrigeration system. The SCP of the cycle with the mass-heat recovery together (combined recovery process) is superior to that of the conventional cycles with mass recovery or heat recovery independently.

Thermal performance analysis of a direct-expansion solar-assisted heat pump water heater

A direct-expansion solar-assisted heat pump water heater (DX-SAHPWH) is described, which can supply hot water for domestic use during the whole year. The system mainly employs a bare flat-plate collector/evaporator with a surface area of 4.2 m 2, an electrical rotary-type hermetic compressor, a hot water tank with the volume of 150 L and a thermostatic expansion valve. R-22 is used as working fluid in the system. A simulation model based on lumped and distributed parameter approach is developed to predict the thermal performance of the system. Given the structure parameters, meteorological parameters, time step and final water temperature, the numerical model can output operational parameters, such as heat capacity, system COP and collector efficiency. Comparisons between the simulation results and the experimental measurements show that the model is able to give satisfactory predictions. The effect of various parameters, including solar radiation, ambient temperature, wind speed and compressor speed, has been analyzed on the thermal performance of the system.

Transient and steady-state experimental investigation of flash tank vapor injection heat pump cycle control strategy

Recent research on vapor injection technique has been mostly focused on performance improvement using different system configurations. The flash tank cycle typically shows better performance than the internal heat exchanger cycle. However, the flash tank cycle control strategy is not yet clearly defined. In this study, a novel cycle control strategy is proposed for an R-410A vapor injection flash tank heat pump system and its feasibility was experimentally investigated. The proposed novel cycle control strategy utilized an electronic expansion valve (EEV) for the upper-stage expansion and a thermostatic expansion valve for the lower-stage expansion, and applied an electric heater in the vapor injection line to introduce superheat to the injected vapor by providing a control signal to the upper-stage EEV. Both transient and steady-state system behaviors were studied. The proposed cycle control strategy was found to be able to provide reliable control to the system.

Application of adaptive control in a refrigeration system to improve performance

This paper reports an experimental investigation using adaptive control in a refrigeration system. This system is composed basically of a semi-hermetic compressor, concentric tubes heat exchangers, the condenser and evaporator, and thermostatic expansion valve (TXV). The refrigerant used in the refrigeration system was the HCFC-22 and also an AC frequency inverter was used to control the speed of the compressor. The temperatures were measured by PT-100 sensors and the pressures using piezoresistive pressure transducers. Data acquisition was implemented using the Labview software. An electronic card with analogical signal output was also used. These analogical signals were converted into digital through a Programmable Logic Controller (PLC) and then sent to the computer through a PC serial port. Tests were performed with a variable speed compressor in the range from 30 to 70 Hz and the experimental results showed that the highest performance (COP) was attained by working in the range of 50 Hz, using adaptive fuzzy control.

Experimental Investigation of Droplet Dynamics and Spray Atomization inside Thermostatic Expansion Valves

Experimental investigation on spray atomization and droplet dynamics inside a thermostatic expansion valve (TEV) was conducted. A needle and an orifice were copied from a commercial TEV and machined to be mounted inside a chamber with optical access so that the flow inside the TEV is simulated and visualized at the same time. The break-up and atomization of the refrigerant were documented near the downstream of the orifice under different feed conditions on micro-second scale. A Phase Doppler Anemometry (PDA) system was used later to measure the size of atomized refrigerant droplets. It is found that spray impingement is inevitable and crucial to the atomization. Under steady-state operation, liquid film was seen formed on the needle plate and caused droplets splashed from plate, which will further have an effect on the droplets size. The before impact and after impact droplets were characterized by PDA system and for studying the impingement. In addition, the impact of the needle geometry inside the valve on refrigerant atomization has also been investigated. * Corresponding author: Chia-fon F. Lee

자동차용 블록식 온도감응 팽창밸브의 모델링

The objective of this study is to propose two empirical correlations to predict the mass flow rate through an automotive block type thermostatic expansion valve and then to evaluate the correlations. The first correlation is deduced by modifying the basic equation of the orifice meter for the mass flow rate and the second correlation is deduced by using the Buckingham's <TEX>${\pi}$</TEX> theorem. The first correlation showed very good agreement on the measured data for R134a, given by Monforte. Average relative deviation and standard deviation of it are 2.5% and 1.6%, respectively. The second correlation agreed on the same measured data with a little greater deviations. The two correlations may apply to common expansion valves which have different geometrical sizes of the same shape.

Research on the control laws of the electronic expansion valve for an air source heat pump water heater

Compared to the conventional air conditioner, the air source heat pump water heater (ASHPWH) possesses wider operating ranges and more dramatic changes in working conditions. Conversely, traditional throttle devices, such as the thermostatic expansion valve (TEV) and capillary tube, are restricted by narrow regulating ranges in refrigerant mass flow rate and lagging response to the superheat. This article incorporates a novel dual-fuzzy-controller to regulate the electronic expansion valve (EEV) specialized for the ASHPWH system. The study analyzes the effects of the EEV initial opening and the target superheat on the performance of the ASHPWH. Moreover, this research proposes a fuzzy control method of selecting the initial opening and the target superheat on the basis of the ambient temperature and water temperature, and employs superheat error ( e) and the derivation of superheat error ( ec) as the input variables of the fuzzy controller B to regulate the opening of the EEV during steady running process. To improve self-adaptability of the fuzzy controller, a rule modifier and a gain scheduler are introduced. In order to quantitatively reflect the difference in the performance between the TEV-controlled system and EEV-controlled one, experimental comparison between the EEV and the TEV is presented. Results demonstrate that both the stability and efficiency of the ASHPWH can be improved significantly by the EEV.

Measured effect of airflow and refrigerant charge on the seasonal performance of an air-source heat pump using R-410A

The objective of this study was to measure the effects of improper airflow and refrigerant charge on the seasonal performance of a typical 10.6 kW, R-410A residential heat pump with a thermostatic expansion valve. Heating and cooling tests were performed in combinations of three refrigerant charges of 75%, 100%, and 125% of nominal value and two airflows of 75% and 100% of rated airflow. In addition, cyclic tests were performed to estimate the heating and cooling seasonal coefficient of performance (COP) at six climate zones specified by Air-Conditioning, Heating, and Refrigeration Institute (AHRI) Standard 210/240-2008. Results showed that, in each climate zone, increases in refrigerant charge at the rated airflow could improve the unit's heating seasonal COP by as much as 5%. However, combined decreases in airflow and refrigerant charge could penalize the unit's heating seasonal COP by as much as 10%.

Experimental Evaluation of System Performance for a Machine Tool Cooler Using Inverter Driven Control

Highly accurate manufacture in machining industry cannot be achieved without precise temperature control of the cooling water. However, the machine tool coolers are facing the control hunting of coolant temperature and the dramatic variation of heat load in high-accuracy machining. In this study, experimental investigation on inverter driven compressor for capacity control has been proposed. Effects of using capillary tube and thermostatic expansion valve along with inverter driven control scheme have been investigated comprehensively. Cooling performance and power consumption of the cooler system have been measured at different frequency (hertz) of inverter under specific cooling water temperature. The experimental results reveal that the inverter driven cooler is cost-effective and energy-efficient for high-precision machine tool cooling.

Experimental investigation of a process cooling system retrofitted with HFC-404A refrigerant for precise manufacturing application

Precise-manufacturing facilities, which emphasize accurate and stable machining of the working components to be used in semiconductor industry, cannot function properly without appropriate and precise cooling. HCFC (hydro-chloro-floro-carbon) has been commonly used as the coolant for precise manufacturing facilities; but it is facing the pressing schedule to be phased out. Additionally, the dramatic variation of heat load during high-accuracy and high-speed applications need a critical control of coolant (brine or water) temperature. Use of eco-friendly HFC 404A to replace HFC has been suggested as an effective alternative to alleviate the problems. In this study, the performance of a process cooling system retrofitted with HFC-404A refrigerant was evaluated; the energy efficiency ratio and accuracy of temperature control specific to −15°C precise manufacturing application were examined. Effects of using thermostatic expansion valve associated with hot-gas by-pass control scheme under different loading conditions have been investigated extensively. The energy efficiency ratio and accuracy of temperature control for the cooling system were measured and analyzed for comparing and evaluating HCFC-22 and HFC-404A using different throttling devices under specific coolant temperatures. The comprehensive studies on improving the accuracy of temperature control and energy-saving efficiencies through different temperature control strategies are presented in this paper.

Residential heat pump heating performance with single faults imposed

Abstract A heat pump equipped with a thermostatic expansion valve (TXV) was tested in environmental chambers during steady-state no-fault and imposed-fault operation. The studied system was an R410A split residential heat pump with an 8.8 kW nominal cooling capacity, Seasonal Energy Efficiency Ratio (SEER) of 13, and Heating Seasonal Performance Factor (HSPF) of 7.8. The imposed faults were compressor valve leakage, outdoor improper air flow, indoor improper air flow, liquid line restriction, refrigerant undercharge, and refrigerant overcharge. Evaporator fouling, condenser fouling, and refrigerant overcharge caused the greatest performance degradation. We observed substantial commonality between sensitive features in the heating and cooling modes; however, several different features were identified for the heating mode as more sensitive.

Thermal analysis of car air conditioning

Thermal analysis of car air conditioningThermodynamic analysis of car air cooler is presented in this paper. Typical refrigerator cycles are studied. The first: with uncontrolled orifice and non controlled compressor and the second one with the thermostatic controlled expansion valve and externally controlled compressor. The influence of the refrigerant decrease and the change of the air temperature which gets to exchangers on the refrigeration efficiency of the system; was analysed. Also, its effectiveness and the power required to drive the compressor were investigated. The impact of improper refrigerant charge on the performance of air conditioning systems was also checked.

Transient characteristics and performance analysis of a vapor compression air conditioning system with condensing heat recovery

The objective of this study is to evaluate the influence of condensing heat recovery on the dynamic behavior and performance of air conditioners. The article includes a test procedure utilized to evaluate the condensing heat recovery system, relevant experimental results, a detail analysis of the mechanisms, and improvement measure on such a system. The experimental results indicate that although the condensing heat recovery has a negative effect on the cooling capacity at the start of the heat recovery process, the average cooling coefficient of performance (COP) of the system can be improved. The study also incorporates a control scheme of the electronic expansion valve (EEV) of the condensing heat recovery system. The experimental comparison between the EEV and the thermostatic expansion valve (TEV) demonstrates that the EEV has better performance in both stability and efficiency in the condensing heat recovery system.

Experimental performance of an automobile air conditioning system using a variable capacity compressor for two different types of expansion devices

An experimental R134a automotive air conditioning (AAC) system with a variable capacity compressor has been developed and equipped with various mechanical instruments. The system has the capability of using both a thermostatic expansion valve (TXV) and an orifice tube (OT) as an expansion device. The system has been tested by varying the compressor speed and temperatures of the air streams entering the condenser (Tcond,ai) and evaporator (Tevap,ai). Using experimental data, the performance parameters of the AAC system for TXV and OT operations have been evaluated. The results show that the cooling capacity usually increases with the compressor speed. However, the exergy destruction in the system also increases and the coefficient of performance (COP) decreases with the compressor speed. The cooling capacity and COP decrease on rising Tcond,ai, while they increase on rising Tevap,ai. The TXV operation usually yields slightly higher cooling capacity and COP and lower exergy destruction compared with OT operation.