Performance investigation of the CO2 gas cooler designs and its integration with the refrigeration system (original) (raw)
Related papers
Modeling and Performance Simulation of a Gas Cooler for a CO2 Heat Pump System
HVAC&R Research, 2007
The outlet temperature of gas cooler has a great effect on the efficiency of carbon dioxide heat pump system. In order to obtain a small approach temperature difference at gas cooler, near-counter flow type heat exchanger has been proposed, and larger heat transfer area is demanded. The optimum design of gas cooler involving the analysis of trade-offs between heat transfer performance and cost is desirable. In this study, a simulation model has been developed for fin-tube type gas cooler, and the air-side heat transfer correlation has been proposed. A developed model was confirmed by experimental results. The effects of geometric parameters, such as the tube arrangement, transverse tube spacing, longitudinal tube spacing and the number of tube rows and fin spacing on the performance of heat transfer were investigated using the developed model. This study suggested various simulation results for optimum designs of gas cooler.
IJERT-Numerical Simulation of Fin and Tube Gas Cooler For Transcritical CO2 Air Conditioning System
International Journal of Engineering Research and Technology (IJERT), 2012
https://www.ijert.org/numerical-simulation-of-fin-and-tube-gas-cooler-for-transcritical-co2-air-conditioning-system https://www.ijert.org/research/numerical-simulation-of-fin-and-tube-gas-cooler-for-transcritical-co2-air-conditioning-system-IJERTV1IS10421.pdf This paper focuses on the development of plain fin and tube gas cooler for CO 2 transcritical air conditioning system operating in subtropical conditions. The numerical simulation is carried out for identification of variation of heat transfer and pressure drop. The thermo-physical and transport properties for CO 2 are taken from NIST database. The simulation study has been carried out for 0.26 kg/sec air mass flow rate and 0.006944 kg/sec refrigerant mass flow rate. The gas cooler pressure of 90 bar at 40 o C dry bulb temperature has been considered. Air side and refrigerant side heat transfer coefficients are estimated and compared with available correlations developed by various researchers viz. Rich, McQuiston, Webb and Gray. Further it is observed that simulation results are having a close matching with correlations from literature.
CFD Modelling of Finned Tube Gas Cooler for Transcritical Operatoon of CO2 Systems
2015
Refrigerators and heat pumps plays an important role in this modern world. Refrigerants are used as working fluid in the thermal systems. These refrigerants undergo phase change in evaporator to provide a cooling effect. Chlorofluorocarbons and Hydroflurocarbons are the commonly used refrigerants but their stability in the atmosphere and their effect on GWP and ODP is a concern. Because of the harmful effects of synthetic refrigerants on the environment, industries are now looking for technologies based on natural refrigerants. Because of non-toxicity, high availability in nature and some unique thermo-physical property CO2 is considered as the replacement for synthetic refrigerants. This facts motivated many and has lead to the development of trans critical cycle where the condenser gets replaced by a gas cooler. Use of the gas cooler with heat rejection taking place with large temperature glide offers several unique possibilities such as such as simultaneous cooling and heating, h...
Applied Energy, 2010
Carbon dioxide is an interesting solution for commercial refrigeration and in perspective for air-conditioning systems. In this paper a newly developed carbon dioxide transcritical air cooled chiller for refrigerating propylene glycol down to À8°C supply temperature is described. The aim of the project was at optimising the cycle energy efficiency while assuring reliable operation and simple management of the unit. The carbon dioxide optimal pressure issue is addressed with an innovate system architecture and control logic. Using a flash tanks and two electronic valves, the optimal cycle upper pressure was maintained in transcritical operation mode. The managing of the valves allows the refrigeration machine efficiency improvement when the gas cooler inlet air allows subcritical working conditions. A simulation model of the chiller was developed and its results validated with experimental data. A measurement campaign was carried out, testing the chiller at external temperatures ranging from 18 to 35°C, the unit energy efficiency ranging from 3.1 to 2.0.
Numerical Simulation of Fin and Tube Gas Cooler For Transcritical CO 2 Air Conditioning System
This paper focuses on the development of plain fin and tube gas cooler for CO 2 transcritical air conditioning system operating in subtropical conditions. The numerical simulation is carried out for identification of variation of heat transfer and pressure drop. The thermo-physical and transport properties for CO 2 are taken from NIST database. The simulation study has been carried out for 0.26 kg/sec air mass flow rate and 0.006944 kg/sec refrigerant mass flow rate. The gas cooler pressure of 90 bar at 40 o C dry bulb temperature has been considered. Air side and refrigerant side heat transfer coefficients are estimated and compared with available correlations developed by various researchers viz. Rich, McQuiston, Webb and Gray. Further it is observed that simulation results are having a close matching with correlations from literature.
Study & Simulation of Co2 Refrigeration System
Carbon-dioxide is not new to refrigeration. Its use began in the mid-nineteenth century and steadily increased, reaching a peak in the 1920s. Its use declined with the introduction of chlorofluorocarbons (CFCs) that operated at much lower pressures. Use of CO 2 continued, but chiefly in cascade systems for industrial and process applications. Recently, strong interest has been shown in CO 2 as a refrigerant by vending machine manufacturers. There are also possibilities for other light commercial refrigeration applications, as well as for residential air conditioning also including the industrial sector applications that involves cold storage.
Numeric simulation of an integrated CO 2 cooling system
2000
In a research project of EADS Airbus and the TUHH a system simulation of a cooling system is to be realized, using the refrigerant carbondioxid (CO2). The simulation models of the cooling cycle are created using Modelica and the thermohydraulic model library ThermoFlow. Modelica and the model library operate since spring 2000. The project will be finished untill the end of 2002. For the structure of the CO2 models so far a FORTRAN program was introduced in Modelica that calculates the state variables of CO2 using an equation of state. Furthermore the heat transfer and pressure loss relations were implemented of CO2 for oneand two-phase and the supercritical status area. Literature reviews of currently measured results were used to check the models. Therefore, the modelling of pipes, evaporators and gascooler/condenser is possible. First results of an uncomplex CO2 -refrigertion cycle are presented and a preview of future work is given.
Environmental concern has become more significant and motivating factor in recent times in design and development of any domestic or industrial products. Consumers have become increasingly aware of the environment and the need to preserve the world in which all live. Concern about ozone depletion has led to the abolition of the use of chlorofluorocarbons (CFCs) and hydro chlorofluorocarbons (HCFCs) as refrigerant. Much of the researchers were reported about the advantage of using CO 2 in trans-critical state. Use of a gas cooler, with heat rejection taking place over an unusually large temperature glide, offers several unique possibilities such as simultaneous refrigeration and heating, heat pump drying, etc. CFD model a finned tube gas cooler for transcritical operation of CO 2 system was developed using ANSYS Fluent 14 to study the effect mass flow rate of CO 2 , fin thickness and tube thickness on the performance of gas cooler. Flow pattern, Temperature distribution and performan...