A Review of the Optimization of Length of Capillary Tube for a Vapor Compression Refrigeration System
28 Mar 2021-Vol. 6, Iss: 2, pp 1-7
TL;DR: In this paper, the effect of capillary tube on the performance of VCR system is discussed, and the results of straight and helical type of Capillary tubes are studied.
Abstract: Vapor Compression refrigeration system is most commonly available system in day to day life from home to malls in India. It is necessary to improve the performance of system. The study is mainly focus on the improvement of performance. Out of different parameter, the literature review covers the effect of capillary tube on the performance of system. It covers the experimental and numerical study on effect of capillary tube. The results of straight and helical type of capillary tubes are studied. The study also covers the CFD analysis for the different length and diameters of capillary tubes and find out the optimize size.
Citations
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TL;DR: In this article, the effects of the relevant parameters on the flow characteristic of R134a and R-22 flowing through adiabatic helical capillary tubes were experimentally studied.
Abstract: Capillary tubes are used as expansion device in low capacity refrigeration machines like domestic refrigerators and window type air conditioners. The advantages of the capillary tube over other expansion devices are simple, inexpensive and cause compressor to start at low torque as the pressure across the capillary tube equalize during the off-cycle. The flow characteristics of refrigerants through capillary tubes have been studied extensively in past six decades, both experimentally and analytically, most of these studies mainly focused on straight capillary tubes. In this thesis, the effects of the relevant parameters on the flow characteristic of R134a and R-22 flowing through adiabatic helical capillary tubes were experimentally studied. The capillary tubes' diameter, coil diameter, and parameters relating to flow conditions such as inlet pressures and degree of sub cooling were the major parameters investigated. In this thesis, the CFD analysis is to determine the heat transfer rate, pressure drop, velocity, mass flow rate and heat transfer coefficient for the fluids R134A and R-22 with different tube and coil diameters. Thermal analysis is to determine the temperature distribution and heat flux for copper and aluminum as tube materials.3D modeling is done pro-engineer and analysis is done in ANSYS software.
2 citations
TL;DR: In this article , the effect of different dimensions of capillary tube on COP, R.E. and power input of water chiller and to find the optimum dimensions for which COP of the system is maximum using experimental results.
Abstract: Capillary tube is most widely used expansion device in the refrigeration system having small applications. It is made up of copper tube having small diameter (0.5–5 mm) & very long length (0.5–5 m). The main aim of this research is to study the effect of different dimensions of capillary tube on COP, R.E. & Power input of water chiller and to find the optimum dimensions of capillary tube for which COP of the system is maximum using experimental results. For this, standard experimental test rig having 2 TR refrigeration capacity was developed in order to perform experimentation on different sets of capillary tubes. The result obtained through this experimentation is used to study the effect of changing dimensions of capillary tube on various performance parameters & to find out the optimum dimensions of capillary tube for 2TR water chiller having R22 & R407C as refrigerants. Also, comparative study between results obtained for R22 & R407C is done. The result obtained through this study is useful to design a capillary tube for 2 TR water chiller (having R22 & R407C as refrigerants) for which performance of chiller is maximum for a given application. As R407C refrigerant is direct substitute for R22, so comparative study will be useful to select and modify the dimensions of capillary tube while replacing the refrigerant with substitute one.
1 citations
References
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TL;DR: In this article, the authors investigated the flow of nanorefrigerants through adiabatic capillary tubes of vapour compression refrigeration systems; and afterwards creates numerical models that will account for solution of refrigerant side pressure drop and mass flow rate.
Abstract: Over time attempts have been made to understand the flow characteristics of refrigerants through capillary tubes as well as to seek more thermally efficient working fluids for refrigeration systems. This study investigated the flow of nanorefrigerants through adiabatic capillary tubes of vapour compression refrigeration systems; and afterwards creates numerical models that will account for solution of refrigerant side pressure drop and mass flow rate. Also in this study, a CFD flow analysis was carried out using a CFD simulation/solver such that the results of the simulations obtained were discussed so as to establish a distinction between the conventional and nano-refrigerants. Upon comparison of the CFD results of nanorefrigerants (CuR134a, CuR600a) and the conventional refrigerants (R134a, R600a), the conventional refrigerants were noticed to have more isothermal regions implying that heat was not being transferred quickly enough to raise the temperature of the adjoining region thus proving that the addition of nanoparticles improves the thermophysical properties of the base fluid. Also, based on the results of the study of the flow patterns of both working fluids, the density of pressure contours in the conventional refrigerants was far larger than that of the nanorefrigerant implying that more compressor work and ultimately greater power will be required. The findings from this study were validated with experimental results showing that a CFD analysis tool/method can be employed to understudy the phenomenal changes that take place in nano-refrigerant movement through capillary tubes without recourse to experimentation.
17 citations
"A Review of the Optimization of Len..." refers background in this paper
...[17] investigated the flow of nano refrigerants through adiabatic capillary tubes of vapour compression refrigeration systems; and afterwards creates numerical models that will account for solution of refrigerant side pressure drop and mass flow rate....
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TL;DR: In this paper, the effect of the geometrical parameters of a vertical conically coiled tube-in-tube (CCTIT) evaporator/condenser and their operating conditions on their effectiveness and on the coefficient of performance (COP) of a vapor compression refrigeration system (VCRS) was investigated.
Abstract: This study experimentally investigates the effect of the geometrical parameters of a vertical conically coiled tube-in-tube (CCTIT) evaporator/condenser and their operating conditions on their effectiveness and on the coefficient of performance (COP) of a vapor compression refrigeration system (VCRS). Twelve CCTIT evaporator/condenser of different taper angles (0–135°) and torsions (0.0777–0.1311) are tested for different water Dean numbers in their annuli, while R134a flows in their internal tube in a counter flow configuration. The results show that increasing the evaporator/condenser taper angles and torsions in addition to decreasing their water Dean numbers augment the evaporator/condenser effectiveness and the COP of the VCRS. However, the coils taper angles have the more dominant effect than the other studied parameters. Finally, experimental correlations are developed to predict the COP of the VCRS in addition to the effectiveness of both the evaporator and condenser as functions of the investigated parameters.
16 citations
"A Review of the Optimization of Len..." refers background in this paper
...[14] experimentally investigates the effect of the geometrical parameters of a vertical conically coiled tube-in-tube (CCTIT) evaporator/condenser and their operating conditions on their effectiveness and on the coefficient of performance (COP) of a vapor compression refrigeration system (VCRS)....
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TL;DR: In this paper, a typical household refrigerator with corresponding fresh food and freezer compartments was replaced with a refrigerant-to-water condenser, which allowed the condensation conditions to be controlled and, second, the estimation of the refrigerant conditions at the condenser outlet from the heat exchanger balance.
Abstract: The capillary tube with a liquid-to-suction heat exchanger (CT-LSHX) is a component that is widely used in household refrigerators. Recent works have indicated that even when measuring subcooled conditions at the condenser outlet, the condition at the capillary tube inlet is a two-phase flow. The present work was dedicated to analyzing the actual refrigerant conditions at the capillary tube inlet and to investigating how full liquid conditions could be achieved. The research was performed using a typical household refrigerator with corresponding fresh food and freezer compartments, replacing the original refrigerant-to-air condenser with a refrigerant-to-water condenser. This allowed, first, the condensation conditions to be controlled and, second, the estimation of the refrigerant conditions at the condenser outlet from the heat exchanger balance. The obtained results indicated the presence of a non-equilibrium two-phase flow, composed of subcooled vapor and subcooled liquid, at the capillary tube inlet, with both liquid and vapor entering the capillary tube as a vortex with small, fast fluctuations of the liquid level. This non-equilibrium indicated that the subcooling, evaluated from the pressure and temperature of the refrigerant at the condenser outlet, was only apparent and did not allow the evaluation of the actual enthalpy. Finally, by using a smaller capillary tube diameter and increasing the compressor speed, full liquid conditions at the capillary tube inlet were achieved. Furthermore, a performance comparison between the original and the new design revealed that the COP was higher with full liquid conditions.
8 citations
"A Review of the Optimization of Len..." refers background in this paper
...[19] works have indicated that even when measuring subcooled conditions at the condenser outlet, the...
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01 Feb 2018
TL;DR: In this article, an attempt is made to analyze the flow of Isobutane (R-600a) inside the coiled capillary tubes for different load conditions by homogeneous equilibrium model.
Abstract: Capillary tubes are simple narrow tubes but the phase change which occurs inside the capillary tubes is complex to analyze. In the present investigation, an attempt is made to analyze the flow of Isobutane (R-600a) inside the coiled capillary tubes for different load conditions by Homogeneous Equilibrium Model. The Length and diameter of the capillary tube not only depend on the pressure and temperature of the condenser and evaporator but also on the cooling load. The present paper investigates the change in dimensions of the coil capillary tube with respect to the change in cooling load on the system for the constant condenser and evaporator conditions. ANSYS CFX (Central Florida Expressway) software is used to study the flow characteristics of the refrigerant. Appropriate helical coil is selected for this analysis.
8 citations
"A Review of the Optimization of Len..." refers methods in this paper
...Alok and Sahu [18] investigated an attempt is made to analyze the flow of Isobutane (R-600a) inside the coiled capillary tubes for different load conditions by Homogeneous Equilibrium Model....
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TL;DR: In this paper, the experimental investigation of a household refrigerator was calculated by simultaneously changing the refrigerant charge (mr) and length of capillary tube (Lc) at different evaporator temperature (Te).
Abstract: In the present work the experimental investigation of a household refrigerator was calculated by simultaneously changing the refrigerant charge (mr) and length of capillary tube (Lc).The recent literature review shows the consistent research in the field of new refrigerants for usage in the refrigeration and air conditioning systems due to increased need and importance on the climate change effects faced by the humankind. The recent decades show the replacement of CFCs with HFCs, later with mixture of HFCs. But the high GWP value of HFCs paved the way for the development of new refrigerants using Hydro carbons or hydrocarbon mixtures. The present paper presents the experimental investigations on the domestic refrigerator using two different hydrocarbon mixtures, viz., R50/50(R290/R600a) and R436Awith mass fraction of 56/44of R290 and R600a. The experiments are conducted by changing the refrigerant charge (mr) and length of capillary tube (LC) at different evaporator temperature (Te).Continuous consecutive lyand cycling tests are performed on the refrigerator under steady state situations. The pressure at the inlet and outlet of the compressor are note down and evaluated as well as the temperature readings can be observed at various positions in the refrigerator. And also the pull down time is noted for the three different refrigerants for varying refrigerant charge and length of capillary and graphs are plotted. The results show that the design temperature of -150C(according to IS1476 part1) and pull down time of 90 minutes are achieved by using 70g of R436A with L=4.5M,for CARE is achieved at pull-down time of 100minutes with 70g and L=5m and R134a achieved as 110minutes with 100g and 4m. The performance has shown that the R436A refrigerant can be the best substitute to R134a.
6 citations
"A Review of the Optimization of Len..." refers methods in this paper
...[7] present work the experimental investigation of a household r refrigerator was calculated by simultaneously changing the refrigerant charge (mr ) and length of capillary tube (Lc)....
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