China
Africa
Explore chapters and articles related to this topic
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.
Heating, Ventilating, and Air Conditioning Systems
Published in Barney L. Capehart, Wayne C. Turner, William J. Kennedy, Guide to Energy Management, 2020
Barney L. Capehart, Wayne C. Turner, William J. Kennedy
Room air conditioners and electrically powered central air conditioners with capacities up to 20-30 tons (or up to 100 tons with multiple compressors) operate using the basic vapor-compression cycle which is illustrated in Figure 8-3. There are four main components in a refrigeration unit using the vapor-compression cycle: the compressor, the condenser, the expansion valve (or control valve) and the evaporator. There is also a working fluid which provides a material that experiences a phase change from liquid to gas and back in order to move heat from one component of the system to another. The working fluid was historically a chlorofluorocarbon or CFC, but producing these CFCs has been phased out because of the damage they cause to the ozone layer. Hydrofluorocarbons or HFCs, or Hydrogen-CFCs or HCFCs are already in use in systems. The current substitutes are R-123 and R-245ca for R-11 and R-134a for R-12. Another short-term remedy is to use halogenated chlorofluorocarbons (HCFC) such as the commonly used R-22 or a mixture of R-22 with other compounds (i.e., near azeotropic compounds). HCFC compounds have less ozone depletion potential (ODP) than CFC compounds (i.e. ODP of R-11 is 1.0 by definition). For example, R-22 has an ODP of 0.05. HCFC production is slated to be phased out by 2030, but there is pressure to accelerate the timetable.
Refrigeration Cycles
Published in Kavati Venkateswarlu, Engineering Thermodynamics, 2020
Consider the different eco-friendly refrigerants such as hydrofluorocarbons (HFCs) that include HFC-32, HFC-134a, HFC-152a, and simple hydrocarbons (HCs) that include propane (R-290), isobutene (R-600a), and propylene for refrigeration and air-conditioning systems, and evaluate their cost, availability, properties, and global warming potential. Prepare a PowerPoint presentation with your recommendations on each of these refrigerants for a particular application.
Review on performance analysis in diffusion absorption refrigeration system (DARS) using different working fluids
Published in International Journal of Ambient Energy, 2023
Sreenesh Valiyandi, Gireeshkumaran Thampi
Nowadays, refrigeration system is used for many purposes, and these are highly effective, need less maintenance, and provide enhanced performance. Normally, ammonia-water mixture and Lithium bromide-water mixtures are used as the working fluid in the refrigeration system. The ammonia-water mixture gives a better performance than the Lithium bromide solution. It is due to the minimum boiling point of NH3 (less than zero degrees). These two methods are highly used in absorption to renovate and improve the refrigeration system (Wu, Xu, and Jiang 2018). Absorption and compression are the two types of refrigeration systems. Here the compression system needs high electricity and high external work and also causes depletion in the ozone layer. These are the disadvantages of the compression system. By comparing these types, absorption techniques give the best performance of the refrigeration system. The absorption system has no external work, less running cost, and less electricity. Chlorofluorocarbon (CFC) refrigerant has not been used in this system, so it has less ozone layer depletion. However, the absorption system is not used commercially because of its low performance (Talpada and Ramana 2019).
Experimental and numerical investigation of thermal performances of R290 and R1234yf refrigerants in a cold room
Published in Science and Technology for the Built Environment, 2022
Mehmet Das, Oguzhan Pektezel, Erdem Alic
Refrigeration applications are highly used in industrialized countries. Although there have been several methods to acquire required cooling, most refrigeration systems are based on vapor compression systems. Refrigeration is among the main contributors to energy consumption globally, and 17% of energy consumption in the world originates from these systems (Ozsipahi et al. 2022). For this reason, improvement of the energy performance of refrigeration systems is an important situation in terms of rational use of energy. The decrease in fossil fuels and the slow development of renewable energy technologies have made the optimum operation of the cooling system important in terms of energy consumption. The compressors cause the most significant share of energy consumption in refrigeration systems. Reducing the electricity consumption of the compressors and making them more efficient with new generation refrigerants are among the primary efforts of the refrigeration industry. When the studies on the energy consumption values of the new generation gases are examined, it is seen that they have lower energy consumption than the old generation gases. As a result of the studies examining the energy consumption of new generation low GWP refrigerants, Berkah Fajar et al. (2020) found that the refrigerant with the lowest energy consumption in the same cooling system was R290 in comparison with R410A. Oruç and Devecioğlu (2018) found that R1234yf refrigerant showed lower energy consumption than R22 in the same cooling system.
Modeling of vertical ground heat exchangers
Published in International Journal of Green Energy, 2021
Seama Koohi-Fayegh, Marc A. Rosen
Heat pumps use the same mechanical principles as refrigerators. While refrigerators remove heat from the interior and discharge it to the environment, heat pumps take heat from the environment and concentrate it to heat the building in the summer. A heat pump is a machine that transfers heat from a source to another region by employing a refrigeration cycle. Although heat normally flows from higher to lower temperatures, a heat pump reverses that flow and acts as a “pump” to move the heat. Therefore, a heat pump can be used both for space heating in the winter and for cooling (air conditioning) in the summer. In the refrigeration cycle, a refrigerant (known as the “working fluid”) is compressed (as a liquid) then expanded (as a vapor) to absorb and remove heat. The heat pump transfers heat to a space to be heated during the winter period and, by reversing the operation, extracts (absorbs) heat from the same space to be cooled during the summer period.