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Refrigeration Cycles and HVAC Systems
Published in S. Bobby Rauf, Thermodynamics Made Simple for Energy Engineers, 2021
A refrigerant is a substance or medium used in a refrigeration system heat cycle. Refrigerants allow heat exchange and work to be performed in refrigeration systems as they undergo repetitive and cyclical phase changes from liquid to vapor and vapor to liquid, as illustrated in Figure 11-5.
Lexicon
Published in Samuel C. Sugarman, HVAC Fundamentals, 2020
refrigerant: (Refrigeration) Any substance that acts as a cooling agent by absorbing heat from another body or substance. Fluids that change from a vapor to a liquid and back to a vapor. Fluids used in refrigeration systems to absorb heat by evaporation (vaporization) and release heat by condensation. The refrigerant for absorption chillers will typically be water with lithium bromide as the absorbent, or ammonia as the refrigerant with water as the absorbent.
Energy-efficient thermal energy generation and distribution in buildings
Published in Paul Tymkow, Savvas Tassou, Maria Kolokotroni, Hussam Jouhara, Building Services Design for Energy-Efficient Buildings, 2020
Paul Tymkow, Savvas Tassou, Maria Kolokotroni, Hussam Jouhara
Refrigerants are the working fluids in refrigeration and heat pump systems. Currently the refrigerants employed in most commercial systems are hydrofluorocarbons (HFCs). HFCs have high global warming potential (GWP), and to control emissions from fluorinated greenhouse gases (F-gases), the European Union introduced the F-gas regulations in 2016 to limit emissions and eventually eliminate the use of F-gases. The original F-gas regulations were revised limiting the total amount that can be sold in the EU to one-fifth of 2014 sales by 2030 and banning their use in many new equipment where environmentally friendly alternatives are available.
Numerical investigation of flashing of propane (R-290) in a helical capillary tube
Published in Numerical Heat Transfer, Part A: Applications, 2023
Soumik Bose, Sofen Kumar Jena, Sewan Das Patle
Chlorofluorocarbons (CFCs) and Hydrochlorofluorocarbons (HCFCs) based refrigerants were used in the cooling appliances of the 20th century. Post-Montreal protocol both developed or developing economies of the world agreed to phase-out the use of CFCs refrigerant-based cooling devices to prevent ozone layer depletion. Complying with Montreal protocol, the use of popular CFC-based refrigerants like Dichlorodifluoromethane (R12) is abandoned. Gradually Hydrofluorocarbons (HFCs) based refrigerants like R134a are widely used for cooling applications. Hydrofluorocarbons (HFCs), including Hydrofluoroolefins (HFOs), have no impact on the ozone layer, but they contribute to global warming. Post Rio convection in 1992, the developed economy pledged to reduce the emissions of greenhouse gases in the combat action for climate change. Most of the domestic refrigerators and air conditioners manufactured past two decades use R-134a refrigerants. While R-134a gives an adequate cooling performance, it has a global warming potential (GWP) value of 1430. The Kyoto protocol of 1997, the Copenhagen accord of 2010, and the Paris climate summit of 2016 emphasized rules out of processes leading to greenhouse emissions. As per adopted policies, by 2040 world is going to phase out the use of HFCs in HVACs. There is a greater demand worldwide to find out the suitable alternative refrigerant of R-134a having lower GWP.
Statistical optimization of Closed Loop Pulsating Heat Pipe parameters with R-410a and nanorefrigerant in air conditioning applications
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Aruna Veerasamy, Kanimozhi Balakrishnan, Sirajunnisa Abdul Razack
In order to improve the heat transfer rate, thermal conductivity and reduce the startup time, refrigerants were commercially utilized instead of nanofluids. Refrigerants are substances or mixtures commonly used in heat pumps, air conditioners and refrigerators. Due to global warming and ozone depletion effects, few refrigerants such as R22, R32, R404a, R125, R134a, R141b, R410a, and R600 were used up for the purposes. Shekhar et al (Deng et al. 2017) analyzed three different refrigerants namely R22, R134a, and R600 for their efficiencies in CLPHP. The results displayed that the thermal resistance was directly proportional to heat pipe efficiency and R22 had lower thermal resistance with higher efficiency than R134a and R600. Meanwhile R600 had high thermal resistance and low thermal efficiency at constant power input and filling ratios. Furthermore, to improve the thermal management and cooling rate of refrigeration systems and air conditioners, researchers used nanofluids mixed with refrigerants (nanorefrigerants) and found that the combination of nanofluids and refrigerants hiked the thermal performance, cooling rate and startup time than lone refrigerants. Nanorefrigerants/nanolubricants are recently the pioneer working fluids in heat pump, waste heat recovery system, refrigeration systems and heat pipes applications.
Experimental Study on Effectiveness of Celdek Packed Liquid Desiccant Cooling System
Published in Heat Transfer Engineering, 2018
Rakesh Kumar, Arun Kumar Asati
In conventional air conditioning system, humidity of the air is controlled by cooling it below dew point temperature. Evaporator has to function at low temperature to meet the requirements of latent heat load. Global warming potential of several refrigerants is high and they are responsible for the depletion of the ozone layer. This method of air cooling is ineffective in humid and hot outdoor conditions because reheating to the required temperature is needed. Control of humidity puts an additional load on conventional cooling system and it consumes more energy to meet the load. Different techniques have been discovered to save this high-grade energy and desiccant cooling system as one of the foremost suitable methods. Desiccant systems are used efficiently as a complement to the conventional vapor compression systems to eliminate its latent cooling load. Desiccant dehumidification systems are ecofriendly in comparison to vapor compression air conditioning system. Separate control of temperature and humidity is possible by utilizing desiccants cooling methods [1]. Air dehumidification is an important operation not only in industry but also in comfort cooling as explained by Gandhidasan [2].