scholarly journals Modelling of Refrigerant Distribution in an Oil-Free Refrigeration System using R134a

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4792 ◽  
Author(s):  
Xinwen Chen ◽  
Zhaohua Li ◽  
Yi Zhao ◽  
Hanying Jiang ◽  
Kun Liang ◽  
...  
Keyword(s):  
Global Warming ◽  
Pressure Ratio ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Percentage Error ◽  
Two Phase ◽  
Phase Form ◽  
Compact Heat Exchangers ◽  
Micro Channels ◽  
Low Global Warming Potential

Increasing number of refrigeration units has led to an increase of CO2 emissions and the destruction of the ozone layer. Using low global warming potential (GWP) refrigerants, improving the efficiency of vapour compression refrigeration (VCR) units, and minimising refrigerant leakages can reduce the global warming effect. Investigating the refrigerant distribution under varied operating conditions can provide a deeper understanding of refrigerant charge optimization. This study proposed a model of refrigerant mass distribution in a prototype oil-free VCR system using a linear compressor with variable strokes and R134a. The absence of the oil lubricant allows the adoption of compact heat exchangers, such as micro-channels, so that the total refrigerant charge can be reduced significantly. The predicted total refrigerant charge has a Mean Absolute Percentage Error (MAPE) of 3.7%. The simulation results indicate that refrigerant distributed in the condenser is most sensitive to operating conditions and total refrigerant charges. The refrigerant accumulated in the condenser is 6.8% higher at a total refrigerant charge of 0.33 kg than that of 0.22 kg. For a total refrigerant charge of 0.33 kg, 72.1% of the total refrigerant can accumulate in the condenser. At a fixed pressure ratio, the refrigerant as a two-phase form in the condenser decreases slightly with the increase of compressor strokes, resulting in a larger mass flow rate, thus cooling capacity. The present model can be adapted for optimization of a refrigeration unit and its components.

scholarly journals Refrigerating fluid with a low global warming potential for automotive air conditioning systems in summer

2021 ◽  
pp. 45-45
Author(s):  
Zhaofeng Meng ◽  
Yin Liu ◽  
Dingbiao Wang ◽  
Long Gao ◽  
Junhai Yan
Keyword(s):  
Global Warming ◽  
Global Warming Potential ◽  
Air Conditioning ◽  
Cooling Capacity ◽  
Automotive Air Conditioning ◽  
Discharge Temperature ◽  
Air Conditioning Systems ◽  
Low Global Warming Potential ◽  
Lower Discharge

Refrigerants with low global warming potential (GWP) are much needed in automotive air conditioning systems. This paper compares two refrigerants, R134a (GWP=1300) and R513A (GWP=573) experimentally. The results show that the latter has lower cooling capacity, lower COP and lower discharge temperature than the former, revealing that R513A is a promising replacement of its high GWP partner.

Mini- and Microchannel Research in Sweden

2003 ◽  
Author(s):  
Bjo¨rn Palm
Keyword(s):  
Heat Exchangers ◽  
Single Phase ◽  
Single Channels ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Two Phase ◽  
Compact Heat Exchangers ◽  
Micro Channels ◽  
Parallel Channels ◽  
Institute Of Technology

The purpose of the present paper is to present research and development within the area of mini- and micro channels in Sweden. A review is made of the historical development of highly compact heat exchangers within the country, starting with plate heat exchangers. The main focus is on the research performed at the Royal Institute of Technology, where mini-channel research has been going on since more than ten years. Single-phase flow as well as two-phase flow is treated, both in single channels and in full-size heat exchangers with multiple parallel channels.

Retrofitting of R404a Commercial Refrigeration Systems with R410a and R407f HFCs Refrigerants

2015 ◽  
pp. 260-294 ◽  
Author(s):  
Mauro Gamberi ◽  
Marco Bortolini ◽  
Alessandro Graziani ◽  
Riccardo Manzini
Keyword(s):  
Global Warming ◽  
Low Temperature ◽  
Global Warming Potential ◽  
Experimental Analysis ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Environmental Benefits ◽  
Medium Temperature ◽  
Air Temperatures ◽  
The Eu

This chapter presents an experimental analysis about the retrofitting of two commercial stationary refrigeration systems marketed by an Italian leading company of the sector. Such systems operate both at medium temperature (MT) and low temperature (LT) and they are originally designed to work with the high global warming potential (GWP) hydrofluorocarbon (HFC) R404a fluid (GWP = 3922). The purpose is to investigate the performances of HFCs R410a (GWP = 2088) and R407f (GWP = 1825) chosen as effective alternatives to HFC R404a, due to their compatibility, non-flammability and market availability. Furthermore, such fluids meet the EU restrictions in force in the next future for high GWP HFCs. The experimental analysis compares the performances, in terms of COP and cooling capacity, of R404a and the two identified alternatives under different operating conditions, i.e. chamber and condenser inlet air temperatures. In case of comparable performances, significant environmental benefits are introduced by the adoption of R407f and R410a in the MT and LT refrigeration systems.

scholarly journals Characteristics of R718 Thermal Systems and Possibilities for Implementation in Refrigeration / Heat Pump Systems in Buildings

2020 ◽  
Author(s):  
Aleksandar Gjerasimovski ◽  
◽  
Maja Sharevska ◽  
Natasha Gjerasimovska ◽  
Monika Sharevska ◽  
...  
Keyword(s):  
Heat Pump ◽  
Pressure Ratio ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Thermal Systems ◽  
Flow Rates ◽  
Isentropic Exponent ◽  
Volumetric Cooling ◽  
Phase Out ◽  
Optimum Application

Regulations for CFCs and HCFCs refrigerants phase out and HFCs and HFEs reduction and renewed interest in natural refrigerants (water R718, CO2 R744, ammonia R717, air, hydrocarbons etc.) are discussed. Thermodynamic properties of water (R718) are analyzed and benefits of applicationas well as challenges in the implementation of R718 systems are explained. Deep vacuum operating conditions and low specific volumetric cooling capacity of R718 are peculiarities that cause large and extremely large volumetric flow rates for the temperature range of refrigeration / heat pump air –conditioning applications. The required pressure ratio for a given temperature lift is high. The high value of the water isentropic exponent causes high temperature at the compressor discharge. The specifics in the R718 turbo compressors caused by that reasons are analyzed and the range of optimum application of R718 refrigeration / heat pump systems are estimated

Retrofitting of R404a Commercial Refrigeration Systems with R410a and R407f HFCs Refrigerants

2016 ◽  
pp. 160-192
Author(s):  
Mauro Gamberi ◽  
Marco Bortolini ◽  
Alessandro Graziani ◽  
Riccardo Manzini
Keyword(s):  
Global Warming ◽  
Low Temperature ◽  
Global Warming Potential ◽  
Experimental Analysis ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Environmental Benefits ◽  
Medium Temperature ◽  
Air Temperatures ◽  
The Eu

This chapter presents an experimental analysis about the retrofitting of two commercial stationary refrigeration systems marketed by an Italian leading company of the sector. Such systems operate both at medium temperature (MT) and low temperature (LT) and they are originally designed to work with the high global warming potential (GWP) hydrofluorocarbon (HFC) R404a fluid (GWP = 3922). The purpose is to investigate the performances of HFCs R410a (GWP = 2088) and R407f (GWP = 1825) chosen as effective alternatives to HFC R404a, due to their compatibility, non-flammability and market availability. Furthermore, such fluids meet the EU restrictions in force in the next future for high GWP HFCs. The experimental analysis compares the performances, in terms of COP and cooling capacity, of R404a and the two identified alternatives under different operating conditions, i.e. chamber and condenser inlet air temperatures. In case of comparable performances, significant environmental benefits are introduced by the adoption of R407f and R410a in the MT and LT refrigeration systems.

Experimental Evaluation on Low Global Warming Potential HFO-1336mzz-Z as an Alternative to HCFC-123 and HFC-245fa

2019 ◽  
Vol 11 (3) ◽  
Author(s):  
Shikuan Wang ◽  
Zhikai Guo ◽  
Xiaohong Han ◽  
Xiangguo Xu ◽  
Qin Wang ◽  
...  
Keyword(s):  
Global Warming ◽  
Global Warming Potential ◽  
Power Input ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Cycle Performance ◽  
Promising Alternative ◽  
Discharge Temperature ◽  
Low Global Warming Potential ◽  
Hcfc 123

HFO-1336mzz-Z with low global warming potential (GWP) was considered as a promising alternative of HCFC-123, HFC-245fa in air conditioning (AC) and heat pump (HP), respectively. In order to understand the operation performances of HFO-1336mzz-Z and HCFC-123, HFC-245fa in different working conditions, an experimental setup for testing the refrigeration cycle performance was built. The cycle performances of HFO-1336mzz-Z and HCFC-123 in AC conditions, HFO-1336mzz-Z and HFC-245fa in HP conditions were investigated by experiment. It was found in AC conditions, the discharge temperatures for the systems with HFO-1336mzz-Z and HCFC-123 were lower than 115 °C, the cooling capacity of the system with HFO-1336mzz-Z was 27% less than that with HCFC-123 at least, and the coefficient of performance (COP) of the system with HFO-1336mzz-Z was 0.1 lower than that with HCFC-123; in HP conditions, the discharge temperature with HFO-1336mzz-Z was lower than that with HFC-245fa, the former was never over 115 °C while the latter was up to 126 °C, the power input to the compressor with HFO-1336mzz-Z was 20% less than that with HFC-245fa in the same HP conditions, the heating capacity of the system with HFO-1336mzz-Z was 30–40% less than that with HFC-245fa.

CFD Simulations Devoted to the Study of Fitting Effects on the Phase Distribution in Parallel Vertical Channels

2015 ◽  
Vol 13 (4) ◽  
pp. 551-559 ◽  
Author(s):  
F. Devia ◽  
A. Marchitto ◽  
M. Fossa ◽  
G. Guglielmini
Keyword(s):  
Heat Exchangers ◽  
Single Phase ◽  
Phase Distribution ◽  
Fluid Dynamic ◽  
Operating Conditions ◽  
Two Phase Flows ◽  
Cfd Simulations ◽  
Two Phase ◽  
Compact Heat Exchangers ◽  
Dynamic Performances

Abstract Uneven distribution of phases in plate heat exchangers is a cause of reduction in both thermal and fluid-dynamic performances. With respect to two-phase flows, phase separation in manifolds with several outlets is a complex phenomenon and no general rules are available for predicting the phase distribution at header–channel junctions. The design of compact heat exchangers and their distributors is still based on empirical approaches and both experimentation and numerical analyses are needed for defining the best geometries able to reduce the mass flow rate non-uniformities in parallel channels. In this paper, a series of CFD simulations are carried out to infer the effects of a protrusion fitting (inside the header) on the single-phase distribution in parallel upward vertical channels fed by a common horizontal distributor. The numerical results are compared with both experimental single-phase and two-phase (liquid/gas) experimental data. The effects of the operating conditions are investigated and general conclusions on the differences and analogies between single-phase and two-phase flows in the present problem are discussed.

scholarly journals Energy and Thermal Conductivity Assessment of Dimethyl-Ether and its Azeotropic Mixtures as Alternative Low Global Warming Potential Refrigerants in a Refrigeration System

2021 ◽  
Vol 25 (1) ◽  
pp. 12-28
Author(s):  
Bukola Olalekan Bolaji ◽  
Olatunde Ajani Oyelaran ◽  
Israel Olutunji Abiala ◽  
Tunde Oluwatoyin Ogundana ◽  
Semiu Taiwo Amosun
Keyword(s):  
Thermal Conductivity ◽  
Global Warming ◽  
Dimethyl Ether ◽  
Pressure Ratio ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Refrigeration System ◽  
Environmental Benefit ◽  
Alternative Refrigerants ◽  
Azeotropic Mixtures

Abstract Substituting Hydrofluorocarbons with natural refrigerants in domestic refrigerators will significantly reduce the direct contributions of fluorinated gases to global warming which will be of great environmental benefit. In this study, the performances of dimethyl-ether (RE170) and its azeotropic mixtures (R510A and R511A) in a refrigeration system were assessed theoretically and compare with that of conventional refrigerant. The study revealed that the three investigated alternative refrigerants exhibited significantly good heat transfer characteristics, low pressure ratio, high latent heat in the liquid phase which resulted in their high thermal conductivity and Volumetric Cooling Capacity (VCC). The thermal conductivity of the refrigerants reduces while the evaporating temperature rises and the value obtained for RE170 was the highest among the four refrigerants studied. The Coefficient of Performance (COP) for RE170, R510A and R511A were higher than that of R134a by 6.20, 10.06 and 3.02 % respectively while their power consumptions per ton of refrigeration were lower than that of R134a by 6.99, 11.04 and 1.47 % respectively. In conclusion, dimethyl-ether and its azeotropic mixtures performed better than R134a in that they have higher thermal conductivity, refrigerating effect, VCC, COP, lower power consumption per ton of refrigeration and hence, they can be considered as suitable replacements for R134a in domestic refrigerator.

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