Urgent! Liquid ammonia refrigeration!
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Dear seniors, I need to design a liquid ammonia cooler here. The inlet temperature of the liquid ammonia is -7 degrees, while the temperature of the wort on the secondary side is 95–8 degrees; the flow rate is 3 t/h! What is the heat transfer coefficient of liquid ammonia, and what is the outlet temperature of ammonia gas? Thank you! Urgent need!
This is the first time I’ve seen a situation like yours. What does 95-8 degrees mean? I don’t quite understand. What is wort, then? I can’t quite think of it. Also, if the liquid ammonia inlet temperature is –7 degrees, then your refrigeration system should not have just one stage; it should have at least two stages. The temperature at the inlet is already at -7 degrees, and the temperature at the outlet is even lower; otherwise, the refrigeration stage ahead will be under strain. The conditions you have provided are too few to allow for an accurate calculation.
What the poster is referring to is probably cooling by means of the evaporation of liquid ammonia – using the heat of vaporization resulting from the evaporation of liquid ammonia to cool the wort. I’m not sure how the evaporation process of liquid ammonia is controlled; if it operates at full liquid level, the heat transfer coefficient will be very low
It mainly relies on the latent heat of vaporization of liquid ammonia. Could the conditions be specified in more detail?
The convective heat transfer coefficient on the liquid ammonia side that I found is 1880 W/m-2.K-1. The original poster provided too little information; it seems impossible to answer.
For ammonia refrigeration, it depends on the type of heat exchanger used. If it’s a semi-welded plate heat exchanger, the temperature range for ammonia is from -7 to -7 degrees Celsius. Generally, the K value for ammonia refrigeration is around 2000 W/m²·K-1. In your case, it seems that the ammonia is supplied by a pump. Different supply methods result in different temperatures as well.