[Mechanical Equipment Technology Edition] Daily Question 201709025: Refrigeration Systems
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It does have an impact: when the concentration is low, the freezing point drops, which affects heat transfer; in severe cases, it can even damage the evaporator. When the concentration is high, the heat capacity decreases, which likely increases power consumption. That’s all I know, as I’m new to this field
Low-temperature chillers may freeze when the concentration of the refrigerant brine is low or when the temperature of the brine is low. The concentration of the coolant brine directly affects the evaporation temperature.
It has an impact; a higher concentration can result in lower temperatures
Answer: The supply water temperature of low-temperature brine chillers is determined according to the user’s requirements. It should be noted, however, that the freezing point of saltwater is related to its concentration; therefore, the concentration of the saltwater used must be such that freezing occurs inside the evaporator of the chiller unit. The actual operating temperature should be 5–8°C higher than the freezing point of saltwater. Furthermore, it should be noted that the concentrations of the sodium chloride aqueous solution and the calcium chloride aqueous solution must not exceed their eutectic concentration. The common approach nowadays is to choose the saltwater concentration so that the freezing point is 5–8°C lower than the evaporation temperature of the low-temperature freezer (5–6°C in the case of a water-tank type evaporator, and 6–8°C for a shell-and-tube type evaporator). It is hereby stated that sodium chloride solutions should be used only in refrigeration systems with an evaporation temperature above -16°C, while calcium chloride solutions can be used in refrigeration systems with an evaporation temperature of at least -50°C.
Answer: The supply water temperature of low-temperature brine chillers is determined according to the user’s requirements. It should be noted, however, that the freezing point of saltwater is related to its concentration; therefore, the concentration of the saltwater used must be such that freezing occurs inside the evaporator of the chiller unit. The actual operating temperature should be 5–8°C higher than the freezing point of saltwater. Furthermore, it should be noted that the concentrations of the sodium chloride aqueous solution and the calcium chloride aqueous solution must not exceed their eutectic concentration. The common approach nowadays is to choose the saltwater concentration so that the freezing point is 5–8°C lower than the evaporation temperature of the low-temperature freezer (5–6°C in the case of a water-tank type evaporator, and 6–8°C for a shell-and-tube type evaporator). It is hereby stated that sodium chloride solutions should be used only in refrigeration systems with an evaporation temperature above -16°C, while calcium chloride solutions can be used in refrigeration systems with an evaporation temperature of at least -50°C.