EXPERIMENTAL INVESTIGATION OF A REFRIGERATION SYSTEM WORKING UNDER TRANSIENT CONDITIONS

2014 ◽  
Vol 22 (03) ◽  
pp. 1450013 ◽  
Author(s):  
J. K. DABAS ◽  
SUDHIR KUMAR ◽  
A. K. DODEJA ◽  
K. S. KASANA
Keyword(s):  
Capillary Tube ◽  
Coefficient Of Performance ◽  
Tube Length ◽  
Design Parameters ◽  
Transient Operation ◽  
Refrigeration System ◽  
Transient Conditions ◽  
Cooling Period ◽  
Optimum Selection ◽  
The Impact

The impact of transient conditions along with varied capillary tube length and charge quantity over the performance of a simple refrigeration system under all time transient operations has been investigated in a specially designed experimental setup. A maximum drop of 75% in the coefficient of performance (COP) of the system was recorded by the end of the transient cooling period. The continuous deterioration in performance from start to end of the transient cooling job can be well minimized by the optimum selection of capillary tube length and charge quantity. This paper refers some of the existing methods to determine the appropriate length of the coiled capillary tube and charge quantity for a newly designed refrigeration machine working under steady state conditions and compares the experimental results of transient operation with these. Optimum charge quantity for transient operation in the present study is 3.5% to 5% less than that calculated by the existing analytical and numerical methods. The optimum length of coiled capillary tube for transient operation as found in this experimental study matches approximately with the length predicted by the existing dimensionless correlation on the basis of design parameters as estimated towards the end of the transient cooling period.

Experimental Investigation on Flow Characteristic of Stepped Capillary Tube for Heat Pump Type Air Conditioner with R410A

2014 ◽  
Vol 960-961 ◽  
pp. 643-647
Author(s):  
Yan Sheng Xu
Keyword(s):  
Mass Flow Rate ◽  
Heat Pump ◽  
Mass Flow ◽  
Flow Rate ◽  
Capillary Tube ◽  
Coefficient Of Performance ◽  
Tube Length ◽  
Air Conditioner ◽  
Capillary Tubes ◽  
Tube Assembly

A stepped capillary tube consisting of two serially connected capillary tubes with different diameters is invented to replace the conventional expansion device. The mass flow rate of refrigerant R410A in stepped capillary tubes with different size were tested. The model of stepped capillary tube is proposed, and its numerical algorithm for tube length and mass flow rate is developed. The experimental results show that the performance comparing between stepped capillary tube system and capillary tube assembly system, the cooling capacity is reduced by 0.3%, the energy efficiency ratio (EER) is equal to each other, the heating capacity is increased by 0.3%, the coefficient of performance (COP) is decreased by 0.3%. That is to say, the performance index of the two kinds of throttle mechanism is almost identical. It indicates that the stepped capillary tube can replace the capillary tube assembly in the R410A heat pump type air conditioner absolutely. The model is validated with experimental data, and the results show that the model can be used for sizing and rating stepped capillary tube.

Miniature Vapor Compression Refrigeration Systems for Active Cooling of High Performance Computers

2001 ◽  
Author(s):  
Ali Heydari ◽  
Kathy Russell
Keyword(s):  
Heat Exchanger ◽  
High Performance ◽  
Capillary Tube ◽  
New Technology ◽  
Mathematical Formulation ◽  
Coefficient Of Performance ◽  
Simulation Program ◽  
Vapor Compression ◽  
Refrigeration System ◽  
System Components

Abstract A small refrigeration system for cooling of computer system components is evaluated. A thermodynamic model describing the performance of the cycle along with a computer simulation program is developed to evaluate its performance. The refrigeration system makes use of a miniature reciprocating vapor compression compressor. Due to space limitations in some high performance computer servers, a miniature refrigeration system composed of a compressor, capillary tube, a compact condenser, and a cold-plate evaporator heat exchanger are used. Mathematical multi-zone formulation for modeling thermal-hydraulic performance of heat exchanger for the condenser and evaporator are presented. The throttling device is a capillary tube and there is presented a mathematical formulation for predicting refrigerant mass flow rate through the throttling device. A physically based efficiency formulation for simulating the performance of the miniature compressor is used. An efficient iterative numerical scheme with allowance for utilization of various refrigerants is developed to solve the governing system of equations. Using the simulation program, the effects of parameters such as the choice of working refrigerant, evaporating and condensing temperatures on system components and overall efficiency of system are studied. In addition, a RAS (reliability, availability and serviceability) discussion of the proposed CPU-cooling refrigeration solution is presented. The results of analysis show that the new technology not only overcomes many shortcomings of the traditional fan-cooled systems, but also has the capacity of increasing the cooling system’s coefficient of performance.

scholarly journals Energy and exergy analysis of vapour compression refrigeration system using selected eco-friendly hydrocarbon refrigerants enhanced with tio2-nanoparticle

2017 ◽  
Vol 6 (4) ◽  
pp. 91 ◽  
Author(s):  
Luke Ajuka ◽  
Moradeyo Odunfa ◽  
Olayinka Ohunakin ◽  
Miracle Oyewola
Keyword(s):  
Power Consumption ◽  
Exergy Analysis ◽  
Capillary Tube ◽  
Coefficient Of Performance ◽  
Refrigeration System ◽  
Exergetic Efficiency ◽  
Evaporator Temperature ◽  
Energy And Exergy ◽  
Nano Lubricant ◽  
Energy And Exergy Analysis

The experimental study investigated the energy and exergy performance of a domestic refrigerator using eco-friendly hydrocarbon refrigerants R600a and LPG (R290/R600a: 50%/50%) at 0, 0.05, 0.15 and 0.3wt % concentrations of 15nm particle size of TiO2 nano-lubricant, and R134a. The effects of evaporator temperature on power consumption, coefficients of performance, exergetic efficiency and efficiency defects in the compressor, condenser, capillary tube and evaporator of the system were examined. The results showed that LPG + TiO2 (0.15wt %) and R600a + TiO2 (0. 15wt %) had the best of performances with an average of 27.6% and 14.3% higher coefficient of Performance, 34.6% and 35.15% lower power consumption, 13.8% and 17.53% higher exergetic efficiency, a total exergetic defect of 45.8% and 64.7% lower compared to R134a. The exergetic defects in the evaporator, compressor, condenser, and capillary tube were 38.27% and 35.5%, 49.19% and 55.56%, 29.7% and 33.7%, 39.1% and 73.8% lower in the system when compared to R134a respectively. Generally, the refrigerants with nano-lubricant mixture gave better results with an appreciable reduction in the exergy defect in the compressor than the pure refrigerants, and LPG + TiO2 (0. 15wt %) gave the best result in the refrigeration system based on energy and exergy analysis.

scholarly journals Effect of Titanium Oxide Nanoparticle Additives on R22 Refrigeration System

2019 ◽  
Vol 9 (2) ◽  
pp. 3458-3460
Keyword(s):  
Titanium Oxide ◽  
Tio2 Nanoparticle ◽  
Coefficient Of Performance ◽  
Refrigeration System ◽  
Heat Transfer Fluids ◽  
New Energy ◽  
Oxide Nanoparticle ◽  
Compressor Work ◽  
The Impact ◽  
Cooling Model

To explore the conservation technique for energy resources and making more efficient new energy systems has init iated the demand for usage of Nanoparticle in heat transfer fluids. The study explored the impact of Nanolubricants based on Mineral refrigeration oil and Tio2 Nanoparticle at three various mass concentrations 0.6g/l,024g/l and 046g/l in a vapour confining refrigeration system. Experiments are finalized out to read the important functions of cooling models, like as coefficient of performance (C.O.P), Compressor work and refrigeration effect when titanium oxide (Tio2 ) Nanoparticle are added to the lubricant. The experiment conduced using R22 refrigerant. The process of Tio2 Nanoparticle by the cooling model was raising the cooling level of accuracy and Collaborative of task and reduction of compressor work.

scholarly journals A novel model and design of a MEMS Stirling cooler for local refrigeration

2021 ◽  
Vol 313 ◽  
pp. 10001
Author(s):  
Sylvie Bégot ◽  
Muluken GETIE ◽  
Alpha Diallo ◽  
François Lanzetta ◽  
Magali Barthès ◽  
...  
Keyword(s):  
Microelectromechanical Systems ◽  
Coefficient Of Performance ◽  
Squeeze Film ◽  
Design Parameters ◽  
Cooling Power ◽  
Macro Scale ◽  
Stirling Engines ◽  
Parametric Studies ◽  
Scale Design ◽  
The Impact

In this paper, we present a new model design and parametric studies of a miniature Stirling cooler machine for on-site refrigeration. The MEMS (Microelectromechanical systems) technology is investigated to design this machine. The concept could be used to provide cooling at chip scale and mitigate hot spots in electronic devices. Whereas numerous works deal with Stirling engines at a macroscopic scale, only a few works concern miniaturized Stirling engines. Therefore, a model analysis giving insights of the impact of the technological choices and downsizing of the machine is needed. A base design model is presented. The model results lead to a cooling power of 10 mW and a Coefficient Of Performance of 1.45. A parametric study is conducted for operational and design parameters. Compared to macro-scale design, the same trend is observed for the influence of the thermal performance regenerator. Different trends from macroscopic engines were observed for hysteresis losses importance, and the choice of the working gas. The raise in power due to the raise in frequency expected for micro-scale devices is counterbalanced by the degradation of the COP due to the increase in thermofluidic losses. Squeeze film damping and finite speed losses can be neglected at this scale.

scholarly journals EFEK VARIASI BEBAN PENDINGINAN TERHADAP COEFFICIENT OF PERFORMANCE (COP) MESIN PENDINGIN PADA BOX COOLER ALAT DISTILASI

2021 ◽  
Vol 8 (2) ◽  
pp. 110
Author(s):  
Ahmad Akromul Huda ◽  
Karyanik Karyanik ◽  
Earlyna Sinthia Dewi
Keyword(s):  
Capillary Tube ◽  
Engine Performance ◽  
Study Data ◽  
Office Building ◽  
Coefficient Of Performance ◽  
Cooling Load ◽  
Refrigeration System ◽  
Pressure Data ◽  
Load Variations ◽  
Temperature And Pressure

Refrigerator has been widely used by the community and can be found in almost every shop, office building and household. The application of refrigeration machines can also be developed in many other equipment and machines, one of which is in the distillation apparatus. Distillation is a method of separating two substances. A distillation machine using a cooling machine in the condenser will be very helpful, especially for distillation. This study aims to determine the effect of cooling on the performance of the cooling machine. Cooling engine performance coefficient of achievement (COP). Load variations are carried out by adjusting the boiler temperature using a thermostat. In this study, data on the temperature and pressure of the refrigerant flowing in the refrigeration system were taken at four points, namely before entering the compressor, before entering the capillary tube and before entering the evaporator . In this study also used four variations of the cooling load given to the box cooler of 110 °C, 125 °C, 140 °C, and 155 °C. Then the temperature and pressure data is processed to get the COP value every time from all variations of the cooling load. The results showed that the increaseing in the cooling load, the smaller the COP value of the cooling machine. In its effect on the length of time the COP value of each variation of the cooling load increases. The highest COP value in this study was obtained at a cooling load temperature of 110 ºC of 10.69 and the lowest was obtained at a temperature of 155 ºC of 9.38.

Experimental Analysis of R134a/LPG as Replacement of R134a in a Vapor-Compression Refrigeration System

2017 ◽  
Vol 25 (02) ◽  
pp. 1750015 ◽  
Author(s):  
Jatinder Gill ◽  
Jagdev Singh
Keyword(s):  
Experimental Analysis ◽  
Capillary Tube ◽  
Energy Performance ◽  
Tube Length ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Experimental Conditions ◽  
Discharge Temperature ◽  
Wide Range ◽  
Vapor Compression Refrigeration

This paper presents an experimental analysis of a vapor compression refrigeration system (VCRS) using the mixture of R134a and LPG with mass fractions of 28:72 as an alternative to R134a. In this work, we compare the energy performance of both refrigerants, R134a/LPG (28:72) and R134a, in a monitored vapor compression refrigeration system under a wide range of experimental conditions. So, the System with R134a/LPG (28:72) was tested by varying the capillary tube length and refrigerant charge under experimental conditions. Performance comparisons of both the systems are made taking refrigerant R134a as baseline, and the results show that the compressor power consumption, compressor discharge temperature and pull down time obtained with R134a/LPG (28:72) of 118[Formula: see text]g and capillary tube length of 5.1 m in vapor compression refrigeration system are about 4.4% 2.4% and 5.3%, respectively, lower than that obtained with R134a in the studied range. Also, when using R134a/LPG (28:72), the system shows values of refrigeration capacity and COP are about 10.6% and 15.2% respectively, higher than those obtained using R134a, In conclusion, the mixing refrigerant R134a/LPG proposed in this study seems to be an appropriate long-term candidate to replace R134a as a new generation refrigerant of VCRS, because of its well environmentally acceptable properties and its favorable refrigeration performances.

Near-Field Electroluminescent Refrigeration System Consisting of Two Graphene Schottky Diodes

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Jaeman Song ◽  
Junho Jang ◽  
Mikyung Lim ◽  
Jungchul Lee ◽  
Seung S. Lee ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Near Field ◽  
Schottky Diodes ◽  
Electrical Power ◽  
Coefficient Of Performance ◽  
Semiconductor Diode ◽  
Design Parameters ◽  
Refrigeration System ◽  
Surface Polaritons ◽  
Light Emitting

Abstract It has been shown that the performance of a thermal radiative device, such as a thermophotovoltaic (TPV) and an electroluminescent (EL) refrigerator, can be significantly enhanced when the vacuum gap between a reservoir and a semiconductor diode becomes nanoscale. Recently, several studies have reported the integration of a TPV and a light emitting diode (LED) in one near-field thermal radiative device to improve the operation efficiency. However, surface polaritons were hardly exploited in previous research because bare semiconductor diodes were used. In this paper, we propose a TPV-LED integrated near-field EL refrigeration system consisting of two graphene-semiconductor Schottky diodes. A substantial refrigeration rate (101.9 kW/m2) is achieved owing to the coupling of surface plasmon-phonon polaritons excited by a symmetric configuration of graphene-polar materials. Moreover, the cooling coefficient of performance (COP) of the system can be enhanced up to 2.65 times by recycling the electrical power generated in the TPV cell. The cooling performance is further investigated in relation to design parameters, namely the doping concentration of Si and insulator thickness.

Thermoeconomic Diagnosis Applied to the Transient Operation of a Microturbine

2012 ◽  
Author(s):  
Vittorio Verda ◽  
Giorgia Baccino
Keyword(s):  
Linear Model ◽  
Energy Resource ◽  
Energy Systems ◽  
Transient Operation ◽  
Main Interest ◽  
Additional Energy ◽  
Transient Conditions ◽  
The Neural Network ◽  
Different Types ◽  
The Impact

The use of thermoeconomic analysis for the diagnosis of malfunctions causing efficiency reductions in energy systems has been widely discussed in the literature. The main objectives of thermoeconomic procedures are to discover malfunctions, locate the components where they have taken place, help one to identify the possible causes and quantify the impact in terms of additional energy resource consumption. In this paper, thermoeconomic diagnosis is applied to discover possible malfunctions of a microturbine. The procedure consists in the use of compact productive models of the components, which relate their exergetic products to their resources. Two different types of productive models are used: linear model and non linear model. The latter is built using neural networks. The main interest in the proposed application is that transient operation of the system is investigated. Results show that diagnosis can be performed both in steady state and transient conditions. The neural network model allows one to detect the anomaly with better accuracy than the linear model.

Thermal analysis on optimizing the capillary tube length of a milk chiller using DC compressor operated with HFC-134a and environment-friendly HC-600a refrigerants

2019 ◽  
Vol 234 (4) ◽  
pp. 297-307
Author(s):  
Shaji Sidney ◽  
Rajendran Prabakaran ◽  
Mohan Lal Dhasan
Keyword(s):  
Thermal Analysis ◽  
Power Consumption ◽  
Capillary Tube ◽  
Exergy Efficiency ◽  
Coefficient Of Performance ◽  
Tube Length ◽  
Capillary Length ◽  
Environment Friendly ◽  
Hfc 134A ◽  
Refrigeration Capacity

In this work, the thermal analysis on optimizing the capillary tube lengths of a dual circuit refrigeration system was carried out experimentally. Two refrigeration circuits were individually operated using two DC powered compressors (HFC-134a and HC-600a) instead of conventional AC powered compressors. The capillary tube optimization was done to maximize the coefficient of performance and exergy efficiency. From the results, it was found that the power consumption and the refrigerant mass flow rate decreases with the increase of capillary tube length for both the HFC-134a and HC-600a circuits, while the refrigeration capacity and coefficient of performance increased up to the capillary tube length of 4.57 m and then decreased. The maximum refrigeration capacity, ice formed, power consumption, and coefficient of performance experienced in the HC-600a circuit were 9.65%, 19.03%, 3.53%, and 7.34% lower than those of the HFC-134a circuit at the optimum capillary tube length. It was also found that at the optimum capillary length, the COP was maximum for the HFC-134a circuit while the exergy efficiency was maximum for the HC-600a circuit. The exergy efficiency of the HC-600a circuit was 11.13% higher than that of the HFC-134a circuit. At the optimum capillary tube length, the total equivalent warming impact values of the HFC-134a and HC-600a circuits were 961.13 kg CO2-eq and 785.77 kg CO2-eq, respectively.

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