Modified Refrigeration System Research Articles

The Effect of Compressor Speed Variation and Vapor Injection on the Performance of Modified Refrigeration System

This work presents an experimental and numerical investigation of vapor compression refrigeration system performance with variable speed compressor and vapor injection. A test rig of 5 ton capacity split air conditioner equipped, with frequency inverter to control the speed of scroll type compressor, and a secondary capillary tube to expand the refrigerant in the vapor injection circuit are used to conduct the experimental work. Three different vapor injection mass ratios (2, 3, and 4%) are investigated with variable compression speed for frequency range from 35 to 60 Hz. TRNSYS-16 is the software is used to simulate a single zone building conditioned with the modified split air conditioner. The results showed that, the reduction of the compressor speed to the frequency of 35Hz leads to an improvement of the COP by 36% and reduces the power consumption by 18%, compared to the conventional refrigeration system. The usage of the vapour injection with variable speed compressor has improved the COP of the modified system by 47% at 35 Hz and 2% vapour injection ratio. The average improvement in cycle capacity at different compressor speeds is about 24.6%, 28.77% and 34.28% respectively for the vapor injection ratios of 2%, 3& and 4%. It was observed that the reduction of compression speed can extend the compressor lifetime by reducing the ON/OFF cycle of the system at a speed of 35Hz and 2% vapor injection by 17.3%, compared to the conventional system. While at a speed of 60Hz, the ON/OFF cycle has increased by 9.3 and 12% for 2% and 4% injection ratios, respectively. The comparison between the numerical and experimental results of the modified system with vapor injection ratio 2% and 35 Hz compressor speed has displayed an increase in the numerical results around 2.57% for COP, 5.8% for cooling capacity and 5.68% for compressor power consumption.

Efek Variasi Beban Pendinginan Terhadap Coefficient Of Performance (Cop) Alat Uji Pengukuran Koefisien Evaporasi Menggunakan Refrigeran R-134A

Investigation of the cooling load effect toward Coefficient of Performance (COP) is important to conduct. The Coefficient of Performance (COP) is related with compressor work and refrigeration capacity in order to produce a refrigeration system which have a high COP. The high COP value can be reached with minimum compressor work, however it has a maximum refrigeration capacity. This research is to know the effect of cooling load variation toward the performance of experimental device of evaporation heat transfer measurement. By knowing the changing of performance toward cooling load variation, it can be useful in design of an effective and efficient air conditioning system.The method of coolecting data is by experimental method that is by varying water mass flowrate (cooling load) which is flowed to evaporator. An evaporator is soak in a 30 xm x 15 cm x 20 cm water box. Water flowrate can be varied and be masured by a water rotameter. Refrigerant is using Freon R-134a. Experiment is conducted with an evaporation heat transfer coefficient device. The device is a model of modified refrigeration system by adding instruments : an orifice, a test section, and an electric heater. Thermocouple and some pressure gauges is installed at some points which has been determined. Thermocouple and pressure gauges is used to collect temperature and pressure data. After conducting an experiment by evaporator cooling load variation, temperature and pressure data is got. Furthermore based on the temperature and pressure data, the enthalpy is got and can be used to counting the compressor power. Refrigeration capacity can be counted from total heat absorbed by evaporator from water and is divided refrigerant mass flowrate. In this research is got results that cooling load given in evaporator enfluences the COP of the experiment device. By increasing in cooling load at the determined variation, the Coefficient of Performance (COP) of the device is increase. In this research it get results increasing of COP at some refrigerant mass flowrate. The maximum result is get at minimum range inverter variation, that is 16 Hz (ṁr = 9,4 g/s - 10,26 g/s) and the maximum cooling load variation is 2 LPM with COP of 4,96. Whereas the minimum results is get at the maximum inverter range variation, that is 24 Hz (ṁr = 11,83 g/s - 12,25 g/s) and the minimum cooling load variation is 1 LPM with COP of 1,98. This research give some information, if a cooling load of an air conditioning room is chanhing, then it will change the parameter (temperature and pressure) and COP of the air conditioning system in a room.

EXPERIMENTAL STUDY OF HOT WATER STORAGE TANKS FROM A DOMESTIC REFRIGERATOR

The extreme necessity to diversify the sources of renewable energy motivates the search for methods of recycling of thermal energy losses of equipments. Thus, these energy losses can be used as a new source of energy for water heating and storage in a Domestic Hot Water Storage Tank (DHWST). Therefore, an experimental apparatus is proposed with a cylindrical tank for liquid storage. The main objective of this experimental test is the estimation of the coefficient of comprehensive energy performance (COP) relative to the system and the analysis of the hot water storage through the stratification technique. The storage and use of this form of energy utilizes a shell and tube heat exchanger, whose function is to condensate the cooling liquid using water in countercurrent, which substitutes the refrigerator finned condenser. Thermal energy losses are collected by the thermosiphon principle, and stored as sensible heat in the tank. The results showed the full operation of the modified refrigeration system as well as the storage of hot water at satisfactory thermal levels for domestic use, since this is a commercially manufactured refrigerator.

Refrigerator COP with thermal storage

Due to the extreme necessity to diversify renewable energy sources, the search for energy recycling methods through the utilization of thermal losses from equipment has become fundamental. Thus, these losses can be used as a new source of energy for water heating and storage in domestic hot water storage tanks (DHWST). For this reason, the construction of an experimental apparatus with a cylindrical thermal storage tank is proposed, in which the objective of the study will be a survey of the coefficient of performance concerning conventional and modified refrigerators, as well as to perform an analysis of hot water, through the thermal stratification technique using a refrigerator with a modified condenser. The collected thermal loss, as per the thermosyphon principle, will be stored as thermal energy. The results showed the full operation of the modified refrigeration system, which did not reveal significant alterations in thermodynamic behavior after the modifications made on the condenser. The dynamic behavior of the thermal distribution was observed through the thermal stratification effect and temperature evolution in terms of time, showing greater variability of the modified refrigerator generating more thermal comfort to users in addition to providing domestic hot water.

Experimental investigation of performance of vapor ejector refrigeration system using refrigerant R123

In the present study, a novel ejector was designed based on a constant area ejector model and manufactured in order to investigate the performance of an ejector refrigeration system in a wider operating range. The ejector, with movable primary nozzle, was mounted on the system that was previously constructed for low pressure refrigerants. The modified refrigeration system has been tested using hot water as driving fluid and R123 as working fluid. The effects of the operating temperatures on the cooling capacity and performance coefficient of the system were investigated experimentally when the primary nozzle position was optimum at the ejector area ratio of 9.97. As a result, a performance coefficient of 0.39 was obtained at the vapor generator temperature 98 °C, the evaporator temperature 10 °C and critical condenser pressure 129 kPa.

Pengaruh Fraksi Udara Terhadap Koefisien Perpindahan Kalor Kondensasi Refrigeran Petrozon Rossy-22 Di Dalam Pipa Tegak

Petrozon Rossy-22 is one of hydrocarbon refrigerants which environmentally safe, since there is no effect on either ozone depletion or global warming. In the refrigeration cycle, imperfect vacuuming process or other factors that permit circulation of air taken place in the system predicted influencing heat transfer rate in condenser. Therefore, research on the influence of air fraction against condensation heat transfer coefficient of Petrozon Rossy-22 inside vertical pipe to be done. A modified refrigeration system of vapor compression was applied in this research, where the condensation was done in the 2 meters straight vertical condenser (double pipe heat exchanger, that further called as test section). The diameter of internal and external pipe were ¾” and 1 ¼” respectively. Electric heater was installed on upstream of the test section. Mixture of air- refrigerant was flowed downward inside internal pipe, while cooling water was flowed upward through annulus. The varied parameters were: air fraction, air-refrigerant and cooling water flow rate. The result of the research indicated that condensation heat transfer coefficient significantly decreased when air fraction increased. The proposed empiric equation is : Nu = 0.0138. (1-w) 8.8198 . Re 0.7941 . Pr 4.7315 with determination coefficient of 0.6927 and average absolute deviation of 17.65 %. The equation was for Re= 6.922-12.953, Pr= 2,008-2,696, and w= (0,25-1)%.

Water heating with heat energy recovered from a refrigerated farm tank

The possibility of recovering heat energy normally dissipated to waste from a prototype 125 gal direct-expansion refrigerated farm tank to heat water for dairy chores was investigated. A 6 ft tall, 1·5 ft dia, 60-gal copper water cylinder, containing a special condenser coil assembly, was connected into the high-pressure side of the standard refrigeration system. The maximum condensing temperature was controlled to 130°F by a pressure switch which could be adjusted to ensure high refrigerant temperatures necessary for water heating while protecting milk cooling performance. A comparison between the daily performance of the original and the modified refrigeration system with the ambient temperature maintained at 70°F showed that 15 gal of water could be withdrawn from the cylinder at 168°F and 40 gal at between 116–130° F when 125 gal of milk were cooled from 95 to 40°F. The useful water heating was equivalent to 17·55 kWh or 11·5 times the additional expenditure of electrical energy required to compensate for the 10% increase of overall cooling time. Halving the cooling load adversely affected the hot water temperatures, however, the advantage derived from using two hot water draw-off points was still apparent. Experimental results confirmed that a simple heat recovery system can also act as a preheater to installed electric dairy water heaters.