Thermostatic Expansion Valve Research Articles

Energetic Assessment of an Electronic and a Thermostatic Expansion Valve for a Variable Capacity Compressor

In this study, a chiller system with an electronic expansion valve (EEV) and a thermostatic expansion valve (TXV) were compared from an energy saving view under variable and fixed speed compressor. The experimental chiller system under study has a variable speed scroll compressor, EEV and TXV, air cooled condenser and auxiliary equipments. The R134a was used in the compressor as a refrigerant. Although in variable speed chiller systems usually EEVs are used, in this study a TXV was also used to compare its performance. The results of the experimental studies show that the chiller system with EEV has 30% lower superheat value and 6% lower power consumption than the chiller system with TXV under variable speed operation. From the fixed speed compressor view, the chiller system with TXV performs 1.7% lower superheat value than the chiller system with EEV and, the chiller system with EEV has 8.5% higher compressor power consumption than TXV.

Influence of the refrigerant charge in an R407C liquid-to-water heat pump for space heating and domestic hot water production

A large number of commercially available domestic heat pumps are being produced without liquid receivers in order to minimize the refrigerant charge. In this type of systems knowing the effect of the refrigerant charge is of prime interest in order to optimize the system performance. This paper presents an experimental study of the influence of the refrigerant charge in an R407C liquid-to-water heat pump for space heating and domestic hot water production. The heat pump consists of a fixed speed scroll compressor, brazed plate heat exchanges and a thermostatic expansion valve. Experimental results are presented for the heating mode of operation at two different water temperatures in the condenser (low and medium temperature applications) with and without domestic hot water (DHW) production in a desuperheater. Results show that an optimum charge that maximized the system COP could be determined. This optimum charge was slightly different when the heat pump was operated for space heating only or for combined space heating and DHW production.

Experimental studies on the performance of mobile air conditioning system using environmental friendly HFO-1234yf as a refrigerant

In this work, the experimental investigation on the performance and exergy analysis of mobile air conditioning system with suction line heat exchanger using environmental friendly HFO-1234yf was carried out under varied evaporator air flow rates. The performance was compared with existing HFC-134a results. The performance analysis showed that the cooling capacity and the coefficient of performance of the system with HFO-1234yf were lower than that of the HFC-134a by upto 2–11%. The power consumption and the volumetric efficiency of the compressor with HFO-1234yf were found to be 14.02% and 11.2% higher than that of HFC-134a. From the exergy analysis, it was observed that the major exergy destruction occurred in the compressor, followed by the condenser, evaporator, thermostatic expansion valve, and suction line heat exchanger for both refrigerants. The exergy efficiency of the system with HFO-1234yf was 2.4–12.6% lower than that of HFC-134a. From this study, it was observed that the losses experienced in the compressor, thermostatic expansion valve and evaporator lead to poor performance with HFO-1234yf.

Comparison between fixed-opening and variable-opening throttling on two-circuit evaporator performance under water maldistribution

Water maldistribution in the two-circuit evaporator was found to induce instabilities, and further deteriorate capacity of the refrigeration system. As a follow-up study, this article presents a comparison between throttling types on the two-circuit evaporator performance under water maldistribution. The evaporator had two circuits of the same specifications, and a fixed-opening valve (FOV) and a thermostatic expansion valve (TEV) were accessed alternatively. Results show that water maldistribution aroused random oscillations in overall outlet temperature/superheat under FOV throttling, and further triggered hunting under TEV throttling and prompted system parameters into periodic oscillations. With water maldistribution increased, oscillation amplitude in overall outlet superheat increased first but decreased later under FOV throttling with the transition from unstable to stable refrigerant flow. However, it kept increasing under TEV throttling due to greater fluctuation in refrigerant supply during hunting conditions. Moreover, capacity of the circuit with larger water flowrate increased monotonously under FOV throttling, but increased first and decreased later after hunting occurred under TEV throttling, which dominated the faster reduction in overall capacity of the two-circuit evaporator in the TEV loop. The comparison suggests that in off-design conditions, variable-opening throttling might perform worse in stability and energy efficiency than fixed-opening throttling.

Vapour compression system analysis undergoing expansion in an ejector

This paper presents the analysis of a vapour compression system undergoing isentropic expansion in an ejector instead of irreversible isenthalpic expansion in conventional expanding devices i.e. capillary tube, thermostatic expansion valve etc. Comparative energy analysis of the optimized ejector expansion vapour compression system (EEVCS) has been done for commercially used refrigerants R134a, R407C and R410A and it is found that the COP enhancement over standard vapour compression system (VCS) is maximum for R410A (11.49%) followed by R407C (10.16%) and least in R134a (9.261%) at fixed condenser and evaporator temperature of 35°C and 5°C respectively. COP of both the systems decreases with the increase in condenser temperature, however the optimized ejector expansion vapour compression system exhibits less drop in its performance as compared to standard vapour compression system at the same condenser and evaporator temperature. The computational analysis has been carried out in Engineering Equation Solver (EES).

Fluid flow modulation in a domestic refrigerative dehumidifier with air-side gearing

Small refrigerative dehumidifiers have shown energy efficiency improvements when operating with air-side gearing. However, the geared domestic dehumidifier has not previously been investigated experimentally for a wide range of airflow settings typical of domestic dehumidifier operation, or with different throttling schemes, and the efficiency of these systems is not well understood under household conditions.In this work, we measure the performance of a commercial domestic dehumidifier, adapted for laboratory testing, in ungeared and geared modes at a wide range of airflows and with both capillary and thermostatic expansion valve throttling to understand how the system performance is effected, for air volume flow rates of 29 L/s - 48 L/s. The measurements show that both capillary and thermostatic expansion valve equipped domestic dehumidifiers can improve energy efficiency in the geared operation mode, but the capillary equipped system is more prone to frosting and wet compression, degrading performance.

Tuning thermostatic expansion valve for implementing suction line heat exchanger in mobile air conditioning system

The suction line heat exchanger is introduced in a mobile air conditioning system in order to achieve higher energy efficiency. Recent studies reveal that improvement in the system with suction line heat exchanger greatly depends on refrigerant properties and operating conditions. In this work, suction line heat exchanger was incorporated in a mobile air conditioning system and the spring force in the block-type thermostatic expansion valve of the modified system was adjusted (1) to match with the cooling capacity and (2) to match with the suction degree of superheat of the original system as two different cases. The refrigerant R134a was used in this study. The optimum charge of the mobile air conditioning system using R134a with suction line heat exchanger was experimentally found to be 740 g which was 19.4% higher than that of the original system. At optimum charge level before tuning the thermostatic expansion valve, the coefficient of performance (COP) of the system was increased by 2.8%, while the cooling capacity was reduced by 6%. After retuning the thermostatic expansion valve to match the original cooling capacity, the COP of the system improved by 11.8% with 10.5% lesser power consumption than that of the original system. With retuned thermostatic expansion valve for the original degree of superheating, the cooling capacity and COP of the system were increased by 6.7% and 16.2%, respectively. From this experiment, it is concluded that the mobile air conditioning system using R134a as a refrigerant with suction line heat exchanger performs better with suitable retuning of thermostatic expansion valve for the same degree of superheating than that is tuned for same cooling capacity.

Performance analysis of a R407C liquid-to-water heat pump: Effect of a liquid–vapor heat exchanger and domestic hot water production

This paper presents an experimental study of a R407C liquid-to-water heat pump for combined space heating (SH) and domestic hot water (DHW) production. The main components of the heat pump are a scroll compressor, a desuperheater for DHW production, two brazed plate heat exchangers (condenser and evaporator) and a thermostatic expansion valve. A liquid–vapor heat exchanger (LVHEx) has been included in order to study its effect on the heat pump performance. Experimental results for typical operating conditions in the heating mode of operation (low and medium temperature applications) are presented and discussed. These operating conditions are combined with simultaneous DHW production at different flow rates and temperature values. Results show that, in general, the COP is higher with simultaneous SH and DHW production than with SH alone. Also, using the LVHEx yields lower heating and compression powers and, in general, slightly lower COP values.

Study and Analysis of Capillary Tube and Thermostatic Expansion valve in Domestic Refrigerator using Eco friendly Refrigerant : A Review

The current review is concerned with the study of the effect of different expansion devices (capillary tube and Thermostatic expansion valve) on the alternative refrigerants used in the domestic refrigerators to have better performance with minimum losses. This paper give the summary and range of various refrigerants used in the refrigeration cycle of global warming which affect the environment by the use of refrigerant, and our aim is to reduce the effect of global warming as well as optimize the performance of domestic refrigerators by using the latest refrigerants and appropriate expansion devices like capillary tube and Thermostatic expansion valve. R134a is used in vapor compression refrigeration system having zero ozone depletion potential (ODP) and almost good thermodynamic properties, but it has a high Global Warming Potential (GWP) of 1300.So many researchers identifying new refrigerants and their blend which are environmental friendly and having low GWP and low ODP. Hydrocarbon refrigerants mainly propane, butane and isobutene are proposed as an environment friendly refrigerants. After reviewing the various literatures on the various expansion devices and hydrocarbons refrigerants and their mixture gives good performance in small capacity domestic refrigerator.

Design of Industrial Water Cooled Chiller for Recycle Cyclohexane in Polyethylene Plant

The research was aimed at providing water for cooling recycled cyclohexane in polyethylene plant to 15°C. This research could be redounding to the benefit of polyethylene plants that are using solution based polymerization technique. A chiller unit of 630 T, which has compressor power input of 378.33 kW and can provide chilled water capable of cooling recycle cyclohexane to 15°C, was designed using Aspen Hysys version 7.1. Four different refrigerants were tested to know the best fit refrigerant for the design and the best among them was R134a. The designed chiller has a coefficient of performance of 6.3 and a capacity greater than that of the defective chiller (550 TR). Unlike the defective chiller, with the increased cooling capacity and corresponding increase in compressor power from 296 kW to 378.6 kW, it could discharge chilled water capable of cooling recycle cyclohexane from 38°C to 15°C without tripping of the unit. With this design, ethylene absorption rate could increase to 40 T/h. Evaporator and condenser were designed and duties were 2166.39 KJ/sec and 2544.72 KJ/sec respectively. A thermostatic expansion valve with flow coefficient of 46.17 gpm was designed. The designed suction and discharge pressure were 414 kpa and 1053 kpa respectively while condenser temperature of 40°C was used for the design. The cooling of recycle cyclohexane from 38°C to 15°C using the chilled water supplied by the designed chiller was simulated using Aspen Hysys.

Thermodynamic analysis of a direct expansion solar-assisted heat pump system working with R290 as a drop-in substitute for R22

The thermodynamic analysis of direct expansion solar-assisted heat pump system working with R290 as a drop-in substitute for R22 was carried out under the metrological conditions of Calicut, India. A prototype of a DXSAHP system consists of a compressor, an air-cooled condenser with evaporator–collector and thermostatic expansion valve. The experiments were carried during the winter months of 2016. The artificial intelligence technique artificial neural network integrated with genetic algorithm model was presented to predict energy and exergy performance of a system. The energy performance ratio of a system was found to be 5.75% higher and reduced heating capacity of about 6.8% when compared to R22. Similarly, the second law analysis (exergy analysis) of a total system working with R290 was found to be better when compared to baseline refrigerant. The selected alternative working fluid is a hydrocarbon and has zero ozone depletion and negligible global warming potential. Hence, R290 can be used as a drop-in substitute for R22 in DXSAHP systems.

Karakteristik Laju Pendinginan Dan Coefficient Of Performance (COP) KTE-2000EV Menggunakan Katup Ekspansi Otomatis Dan Katup Ekspansi Thermostatik

The purpose of the study was to determine the characteristics of the cooling rate and The ideal coefficient of performance (COP) is the KTE-2000 EV refrigeration machine using an automatic expansion valve and thermostatic expansion valves. Analysis of the cooling and COP rates is ideally done by measuring changes in room temperature and plotting data on temperature and compressor pressure on the suction side and press side (suction line and discharge line) in the P-h diagram for the type of refrigerant R-404a. The test results show the characteristics of the average KTE-2000 EV cooling rate using an automatic expansion valve is 0.035 oC / s with an ideal COP value between 1.91 to 2.02, while for the thermostatic expansion valve the cooling rate characteristics obtained are an average of 0.024 oC / s and the ideal COP value between 2.58 and 3.13.

전자식과 온도식 팽창밸브를 적용한 히트펌프의 증발기 열원수 온도 변화에 따른 성능 비교

전자식과 온도식 팽창밸브를 적용한 히트펌프의 증발기 열원수 온도 변화에 따른 성능 비교

Evaluation of gray box thermostatic expansion valve mass flow models

Thermostatic expansion valves (TXVs) are widely used in air-conditioning and commercial refrigeration systems. Accurate predictions of the refrigerant mass flow rate across a refrigeration cycle are desired in many engineering processes and applications such as a computer simulation model, for control purposes, or for fault detection and diagnostics (FDD). Several researchers have developed mass flow models for TXVs. This paper reviews and analyzes four gray-box TXV mass flow models in the literature and evaluates and compares their performance. Three of the models were developed for air-conditioners, but in the current work their applicability to refrigeration system modeling is assessed, with the use of normal and faulted laboratory data from a commercial walk-in cooler and a freezer. Model regression parameters are calculated during the training process with the use of parameter estimation techniques and a training dataset. The models are then used to predict the mass flow rates for several validation data points. Each of the models is found to perform well for the majority of the data points for the freezer, typically with errors below 10%, but application of the models to the cooler's dataset resulted in relatively large errors. The source of the model deviations includes the difficulty associated with the calculation of the TXV diaphragm force and the thermodynamic states of a two-phase refrigerant at the inlet of the valve. The presence of a liquid line receiver, which are common in refrigeration equipment, appears to cause some model deviation.

Performance of hydrocarbon mixture in a direct expansion solar assisted heat pump system

The energy performance of a direct expansion solar assisted heat pump system, working with a hydrocarbon mixture (HCM) of R290/R1270, 70:30 (by mass ratio) was investigated. The experiments were carried out at a metrological condition existing near Calicut, India. The experimental system mainly consists of a compressor, condenser, thermostatic expansion valve and evaporator collector. A system simulation technique was used for modelling the system. The experimental results obtained are compared with simulation output of the system working with R22 and a mixture of R290/R1270. The selected alternative working fluid mixture showed better energy performance ratio about 5.8% higher. The parametric analysis of the system working with R22 and a mixture of R290/R1270 is investigated with the help of an established system simulation model. The effect of an evaporator (solar collector) area and solar insolation are found to be the significant influencing parameters on the system performance. Moreover, the new hydrocarbon mixture is found to be a good energy efficient and environmental friendly working fluid to phase out R22 in the solar assisted heat pump systems.

Flow and thermal management of engine intake air for fuel and emissions saving

Charge air cooling is the typical technique to reduce temperature of the engine intake air, increasing air density and improving cylinder filling and engine volumetric efficiency in present turbocharged diesel engines. Usually, charge air is cooled by environmental air that crosses a heat exchanger placed in front of the vehicle: its cooling capacity is related to the vehicle speed and other constraints (presence of the main radiator). This leads to an intake air temperature from 30 to 80 °C, depending on engine load, external air conditions and vehicle speed again. If the intake air was more cooled down, the engine volumetric efficiency would be further increased. This can only be done by the use of a dedicated cooling fluid, operating at lower temperature with respect to external air. In this paper, therefore, an evaporator, mounted in parallel with the one of the refrigeration unit used for cabin cooling, was placed on the intake line of a turbocharged diesel engine (F1C IVECO engine), tested on a high speed dynamometer bench: the air refrigeration unit is also composed by a compressor, a condenser and a thermostatic expansion valve. The effects of the undercooling of the charge air have been experimental assessed in terms of fuel consumption and regulated emission reduction, evaluated on the most common engine operating points. Mechanical power demand of the compressor has obviously taken into account in order to assess overall benefits. Achieved net fuel consumption is in the order of 1% at fixed conditions operating the engine as a light duty type, when the intake air sub-cooling is turned on. A benefit on the regulated emissions has been observed (Nitrogen Oxides, Soot) regardless of the setup of the engine combustion processes (injection time, fuel distribution for each injection, Exhaust Gas Recirculated rate). Unburned hydrocarbon and Carbon monoxide behavior, on the other hand, deserves some more attention and call for the re-calibration of the previously cited combustion control parameters.

Effects of charge on the performance of R290 air conditioner with different expansion devices

Safety is a critical issue when considering R290 as a replacement for R22 in air conditioning and heat pump systems. The R290 charge mass in the domestic system is strictly restricted which means a small amount of leakage would be equivalent to a large percent of refrigerant loss. In this article, the effects of R290 refrigerant charge influences on a split air conditioning system with different throttling devices including capillary tube, thermostatic expansion valve (TXV), and electronic expansion valve (EEV) are experimentally investigated alongside with the indoor temperature, outdoor temperature and indoor air volume flow rates effects. Besides, the effects of superheat degree influences have been studied both theoretically and experimentally. The results suggested a larger superheat degree would have an optimum effect on R290 system performance.

A novel exergy based charge optimisation for a mobile air conditioning system

In this paper, a novel exergy based charge optimisation technique is proposed instead of coefficient of performance (COP) based method for a mobile air conditioning system. The exergy destructions in each of the components in the system as a function of compressor speed and refrigerant charge level were estimated based on experimental data. It was found that the COP of the system decreases as the compressor speed increases, while the total exergy destruction in the system increases. The exergetic analysis of performance data showed that the percentage loss in the compressor, evaporator, condenser and thermostatic expansion valve lies in the range of 59.88–69.9%, 17.53–25%, 7.80–16.36% and 3.05–15.73%, respectively. Based on COP, the optimum charge varied with respect to compressor speed. The exergy based optimisation is found to be more reliable and consistently yielding a single optimum charge of 620 g irrespective of the compressor speed. The maximum exergetic efficiencies at 620 g were 43.32% and 38.15% for 900 rpm and 1800 rpm respectively.

Capillary Tube and Thermostatic Expansion Valve Comparative Analysis in Water Chiller Air Conditioning

The aims of this study to compares the performance characteristics of a water chiller air conditioning simulation equipped with thermostatic expansion valve (TEV) with those of a capillary tube. Water chiller system filled with the same charge of refrigerant. Comparative analyses were performed based on coefficient of performance (COP) and performance parameter of the refrigeration system, carried out at medium cooling load level with the ambient temperature of 29-31°C, constant compressor speed and fixed chilled water volume flowrate at 15 lpm. It was shown that the TEV system showed better energy consumption compared to that of capillary tube. From the coefficient of performance perspective, the thermostatic expansion valve system showed higher COP (± 21.4%) compared to that of capillary tube system.

Generalized effects of faults on normalized performance variables of air conditioners and heat pumps

The effects of several types of faults on air conditioners and heat pumps have been studied in many laboratory experiments. All available data have been gathered, and the independent variable (fault intensity) and each of the dependent variables (fault impacts) are normalized to show the trends in a generalized fashion. Relationships are provided wherever there are sufficient results. Most of the significant fault types are included (except refrigerant charge variation, which was discussed in Mehrabi and Yuill (2017)): condenser heat transfer (CA), evaporator heat transfer (EA), liquid line restriction (LL), compressor leakage (VL), and non-condensables in the refrigerant (NC). Relationships are presented separately for fixed orifice and thermostatic expansion valve equipped systems. The variation level in the results indicates that in many cases, the generalized relationships provide reasonable predictors of fault effects on systems for which laboratory test results are unavailable. These relationships provide the first generalized fault effect models for air conditioners and heat pumps.