Oil retention in microchannel heat exchangers of an R134a refrigeration system and effects on their energy performance and system COP

2018 ◽  
Vol 25 (3) ◽  
pp. 272-281 ◽  
Author(s):  
Lorenzo Cremaschi ◽  
Ardiyansyah Saad Yatim
Keyword(s):  
Heat Exchangers ◽  
Energy Performance ◽  
Refrigeration System ◽  
Oil Retention

scholarly journals FREON COOLING MINISYSTEM USING CIRCULAR MICRO-CHANNELS

2017 ◽  
Vol 20 (2) ◽  
Author(s):  
LILIANA PĂTULEANU ◽  
IOAN-COZMIN MANOLACHE-RUSU ◽  
TIBERIU BURDAN ◽  
FLORIN ANDRONIC ◽  
IVAN RADION
Keyword(s):  
Processing Speed ◽  
Heat Exchangers ◽  
Mechanical Compression ◽  
Refrigeration System ◽  
Electronic Components ◽  
Local Cooling ◽  
New Methods ◽  
Micro Channels ◽  
Nano Channel ◽  
Set Up

<p>The necessity of a higher data processing speed was crucial for the advances in computer science. There were created processors that needed increasingly more power, so that new methods were discovered and more complex systems were created in order to solve the cooling issue. In this paper, there are presented the trials performed on a mini refrigeration plant that used mechanical compression of Freon’s, designed to cool electronic components like microprocessors, microcontrollers, graphic stations, or in the case of local cooling in diverse areas such as bioengineering, optics and nanotechnologies. The refrigeration system was constructed as an experimental set-up and consists of the following: two mini heat exchangers, working both as a condenser and a vaporizer, which are made of circular micro channels, a refrigeration compressor, lamination valve which contains a circular nano channel and a micro filter. The experimental determinations have proven that, although such a system contains a small quantity of Freon, of the order of milligrams, it reaches temperatures of -44 °C.</p>

scholarly journals Matrix method to solve inverse problem of heat transfer in heat exchangers with phase transition in heat carriers

Vestnik IGEU ◽  
2021 ◽  
pp. 68-75
Author(s):  
A.E. Barochkin
Keyword(s):  
Heat Transfer ◽  
Phase Transition ◽  
Inverse Problem ◽  
Heat Exchangers ◽  
Power Plants ◽  
Thermal Power ◽  
Energy Performance ◽  
Steam Boiler ◽  
Resource Saving ◽  
Heat Carriers

The transition to environmentally friendly and resource-saving energy, efficient use of natural resources and energy performance are the key priorities of the state energy policy of the Russian Federation. Maximum use of heat combustion of fuel and simultaneously production of condensate water of the combustion products of natural gas is one of the directions of energy saving policy. Despite many scientific papers on the issues of utilization of flue gas heat, condensation heat exchangers are not used in most gas boiler houses, energy power providers and thermal power plants in this country. And there are several reasons to explain this fact due to the lack of universal methods to calculate and design condensation-type heat exchangers. Thus, the development of new methods to simulate multithreaded heat exchangers considering the phase transition in heat carriers is an urgent task of power engineering and industry sectors. Matrix models of heat transfer based on mass and energy balance equations are applied to solve the inverse problem of heat transfer in heat exchangers, considering the phase transition in heat carriers. A method to calculate and select the designs of multi-threaded heat exchangers, considering the phase transition in heat carriers, has been developed. The author suggests a numerical solution to choose the design of a contact economizer of a heat power plant steam boiler used for heat recovery of flue gases to illustrate the effectiveness of the proposed method. The proposed method to solve the inverse problem of heat transfer provides the possibility to identify simultaneously the most acceptable values of the parameters of heat carriers and design characteristics of heat exchangers for various purposes.

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.

Energy and exergy analysis of a subcritical cascade refrigeration system with internal heat exchangers using environmentally-friendly refrigerants

2020 ◽  
pp. 1-33
Author(s):  
Cenker Aktemur ◽  
Ilhan Tekin Öztürk
Keyword(s):  
Heat Exchangers ◽  
Internal Heat ◽  
Exergy Efficiency ◽  
Refrigeration System ◽  
Evaporator Temperature ◽  
Discharge Temperature ◽  
Thermodynamic Performance ◽  
Condenser Temperature ◽  
Cascade Refrigeration System ◽  
Cascade Refrigeration

Abstract This study focuses on a thermodynamic performance analysis of a subcritical cascade refrigeration system (CRS) with internal heat exchangers (IHXs) using R41/R601, R41/R602A, and R41/cyclopentane as refrigerant pairs. The effect of evaporator temperature (Tev), condenser temperature (Tcond) and temperature difference in cascade heat exchanger (ΔTCHX) on examined performance parameters are investigated. Each performance parameter is scrutinized by an optimum LTC condenser temperature. The operating parameters have some implications on the overall thermodynamic performance of the system. A change of 10°C in the Tev and Tcond affects the performance of the system by approximately +26% and −8%, respectively. Moreover, a variation of 1°C in the ΔTCHX reduces the performance of the system by about 2%. The effect of IHXs on the system has some interesting results. The COP and exergy efficiency values of the system using R41/cyclopentane tend to constantly decrease by nearly 4.05%. Although not as much as R41/cyclopentane, there is also a slight drop in the performance of other refrigerant pairs. The discharge temperature in LTC and HTC compressors exceeds 120°C for low-temperature refrigeration requirements, which is highly undesirable. Furthermore, the top priority components for the system improvement are HTC condenser, HTC compressor, and CHX. The refrigerant pairs with the thermodynamic performance from best to worst are R41/R601, R41/cyclopentane, and R41/R602A, respectively. Finally, the COP and exergy efficiency values of the modeled system are 10.40% higher and 3.06% lower, respectively, compared to current models in the literature.

scholarly journals F-Gas regulation-Possible solutions for the retrofit dead end

2018 ◽  
Vol 178 ◽  
pp. 09023
Author(s):  
Filipe Gonçalves ◽  
Miguel Cavique
Keyword(s):  
Heat Exchangers ◽  
Air Conditioning ◽  
Refrigeration Cycle ◽  
Refrigeration System ◽  
Air Conditioning System ◽  
Dead End ◽  
Air Conditioning Systems ◽  
The Impact ◽  
Maintenance Problem ◽  
The Eu

The EU F-gas regulation of 2006 and the recast of 2014 are forcing the market to reduce the use of refrigerants with high global warming potential (GWP). As a result, the production of hydrofluorocarbon (HFC) refrigerants with higher GWP decreased, making the prices of all HFC gases to increase. Any maintenance problem in a refrigeration system asks to evaluate the retrofitting of the gas making necessary to know the expected behaviour of the system. This paper aims to discuss the gases that can substitute the now-a-days HFCs, and the impact the retrofit will cause in a real air-conditioning systems. Many studies on retrofit address the behaviour of the refrigeration cycle, but usually, do not take into account the behaviour of the system as a whole. This paper models a water-to-water air-conditioning system taking into consideration the evaporator and condenser heat exchangers, the refrigeration cycle, the air-conditioning loop and the heat exchanger to the acclimatized area. Moreover, the paper studies the performance of the system when subjected to high condensing temperatures. The paper concludes that all possible retrofit solutions need to use flammable gases that make the refrigeration power of the equipment to reduce.

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