[Mechanical Equipment Technology Edition] Daily Question 20171215: Cooling Medium
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This post was last edited by YORK Industrial Refrigeration on 2017-12-18 at 10:03. Starting from now, in order to enhance communication among users, a \"Question of the Day\" activity has been launched on the Mechanical Equipment Technology forum. We hope everyone will participate actively to progress and improve together! ! ! Rewards: 3 points for active participation, 10-15 points for correct answers. This question is valid for two days; no scoring will be given after that period. The fluid that flows in a refrigeration system is a refrigerant. In indirectly cooled refrigeration units, an intermediate cooling medium is used to transfer the heat from the system to be cooled to the refrigerant. This intermediate cooling medium is called the second refrigerant, or in other words, the coolant. What are the commonly used cryogenic fluids? Coolants include water, brine, and organic compounds. Saltwater: sodium chloride, calcium chloride, magnesium chloride. Organic compounds: ethylene glycol, glycerol, methanol, ethanol, dichloromethane, trichloroethylene. ================================ High-quality promotions: Mechanical equipment——Maintenance procedures for York screw compressors https://bbs.hcbbs.com/thread-1806833-1-1.html Mechanical equipment——Upgrading of York Quinton control centers https://bbs.hcbbs.com/thread-1804837-1-1.html Mechanical equipment——Major repairs for GEA Grasso screw compressors https://bbs.hcbbs.com/thread-1800467-1-1.html Mechanical equipment——Disassembly and maintenance of British HOWDEN screw compressors https://bbs.hcbbs.com/thread-1832529-1-1.html Mechanical equipment——Disassembly and maintenance of Japanese Maekawa MYCOM screw compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=
Freon, ammonia. I don’t know anymore
Commonly used cooling media: 1. Water: Water can be used as a cooling medium for operating temperatures above 0°C. Water has a high specific heat, good convective heat transfer properties, and is inexpensive. 2. Brine, which is generally an aqueous solution prepared from calcium chloride (CaCl2) or sodium chloride (NaCl): it can be used as a coolant in applications where the operating temperature is below 0°C. The higher the concentration of brine, the greater its density and the greater the flow resistance ； At the same time, as the concentration increases, its specific heat decreases; as a result, the flow rate of the saline solution required to transfer a certain amount of heat increases, leading to higher power consumption by the pump. Therefore, when preparing a saline solution, it is sufficient to ensure that the freezing temperature corresponding to its concentration is not lower than the lowest temperature that may occur in the system; generally, the freezing temperature is set 5–8°C lower than the evaporation temperature of the refrigerant. Saltwater solutions are also corrosive to metals, especially those that are slightly acidic and in contact with air, as their corrosiveness is even greater in such cases. To reduce the corrosive effect of saltwater on metals, a certain amount of preservative can be added to the saltwater solution ； 3. Organic refrigerants, mainly aqueous solutions of ethylene glycol and propylene glycol. They are all colorless, tasteless, and non-electrolytic solutions. Their freezing points are all below 0°C, and they have no corrosive effect on metal pipes and containers. Propylene glycol is non-toxic and can come into direct contact with food without causing contamination. Ethylene glycol is slightly toxic but harmless, and its price and viscosity are lower than those of propylene glycol.
Generally, saline solutions such as those containing sodium chloride or calcium chloride are used, or aqueous solutions of organic compounds such as ethylene glycol or glycerol are employed
Commonly used cryogens include air, water, brine, and aqueous solutions of ethylene glycol and propylene glycol.
1. Water: Water can be used as a coolant for operating temperatures above 0°C. Water has a high specific heat, good convective heat transfer properties, and is inexpensive. 2. Brine, which is generally an aqueous solution prepared from calcium chloride (CaCl2) or sodium chloride (NaCl): it can be used as a coolant in applications where the operating temperature is below 0°C. The higher the concentration of brine, the greater its density and the greater the flow resistance ； At the same time, as the concentration increases, its specific heat decreases; as a result, the flow rate of the saline solution required to transfer a certain amount of heat increases, leading to higher power consumption by the pump. Therefore, when preparing a saline solution, it is sufficient to ensure that the freezing temperature corresponding to its concentration is not lower than the lowest temperature that may occur in the system; generally, the freezing temperature is set 5–8°C lower than the evaporation temperature of the refrigerant. Saltwater solutions are also corrosive to metals, especially those that are slightly acidic and in contact with air, as their corrosiveness is even greater in such cases. To reduce the corrosive effect of saltwater on metals, a certain amount of preservative can be added to the saltwater solution ； 3. Organic refrigerants, mainly aqueous solutions of ethylene glycol and propylene glycol. They are all colorless, tasteless, and non-electrolytic solutions. Their freezing points are all below 0°C, and they have no corrosive effect on metal pipes and containers. Propylene glycol is non-toxic and can come into direct contact with food without causing contamination. Ethylene glycol is slightly toxic but harmless, and its price and viscosity are lower than those of propylene glycol.
Commonly used cryogens include air, water, brine, and organic substances.
Common cryogens include air, water and saline solutions, propylene glycol and ethylene glycol, dichloromethane, and chlorofluoromethane. There are many types of refrigerants, which can be gases, liquids, or solids.
Air, water and saline solutions, propylene glycol and ethylene glycol, dichloromethane and chlorofluoromethane, etc
Air, water, saline water, organic compounds, and their aqueous solutions, etc