Questions about the freezer
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-For the 25-degree cold water chiller, there is a circulation water tank, an internal circulation pump, and an external circulation pump. A propylene glycol aqueous solution with a concentration of about 50% is used, and both the internal and external circulation pumps are Southern centrifugal pumps. When the refrigerant temperature drops to -18, it seems that the viscosity of the coolant increases and its fluidity decreases (it didn’t seem to be like this before); when the temperature rises, for example to -5, its fluidity improves. The equipment has been in use for half a year; I would appreciate it if someone could help analyze whether the problem lies with the pump or with the coolant. Thank you
The viscosity of coolant changes with temperature: it increases as the temperature drops and decreases as the temperature rises. Centrifugal pumps are high-speed pumps, and they have difficulty transporting liquids with high viscosity. If the person in question can control the temperature of the medium, then using a centrifugal pump is fine; otherwise, a positive-displacement pump such as a gear pump or vane pump could be used. Positive-displacement pumps generally operate at much lower speeds than centrifugal pumps, and they can handle a wider range of fluid viscosities
The viscosity of propylene glycol aqueous solutions increases as the temperature drops, resulting in poorer flowability. Alcohol or saline will work better.