Regarding the temperature issue of liquid ammonia
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The liquid ammonia comes from the cryogenic machine; its temperature is unknown, while the pressure is generally 1.5 MPa. It enters at the lower part of the heat exchanger’s shell. The heat exchange tubes in this exchanger are 6 meters tall and have a diameter of about 1.5 meters. After that, there is a hydrocyclone, with a pressure setting of 0.42 MPa. The liquid ammonia remains at roughly half of its capacity in the shell. What is the temperature of the liquid ammonia at the lower part of the shell under these conditions? If the liquid ammonia first goes into a tank after coming from the cryogenic machine, and then enters a hydrocyclone with a pressure of 0.42 MPa, and an outlet is provided at the lower part of the tank to feed into the lower part of the shell of the tubular heat exchanger, using the same specifications as before and with the same liquid level, then what would be the temperature of the liquid ammonia in this case? This post was last edited by steinback on 2009-2-15 at 23:26
Does it mean that ammonia is in a vapor-liquid two-phase state inside the heat exchanger? In that case, it should be the saturation temperature at the corresponding pressure. The former corresponds to the saturation temperature at 1.5 MPa, which is around 35°C, while the latter corresponds to the saturation temperature at 0.42 MPa, which is around 0°C? I’m not sure if that’s the case.
Ammonia exists in a vapor-liquid phase inside the heat exchanger, but it should not be forgotten that liquid ammonia releases a large amount of latent heat when it evaporates; this heat is drawn from both the tube walls and the liquid ammonia itself. It’s unlikely to be 35 degrees; when we swapped the heat exchangers, we found that the pipelines through which liquid ammonia flowed were very cold. A few degrees, I guess. The two situations, upper and lower, are similar. But I want a more precise calculation. Whoever can figure it out, I’ll do my best to give extra points.
Bro, you haven’t included any diagrams and your description isn’t detailed enough. But based on experience, the temperature after coming out of the chiller is above 60 degrees; at this point it’s not a liquid but a gas – ammonia that has been compressed for cooling. It becomes a liquid after being cooled to normal temperature by the heat exchanger (using circulating water). The process of evaporation you mentioned doesn’t occur at this stage; rather, it’s the opposite process. Unless the heat exchanger you’re referring to is part of the cooling system, in which case the temperature will definitely be low. The temperature is determined by the pressure of the gas phase in the user’s heat exchanger. As for the situation you described when the heat exchanger is reversed, it happens because liquid ammonia evaporates after depressurization, and that’s when such a phenomenon occurs. You’re referring to a chiller, right????:(
Bro, the heat exchanger I’m talking about refers to those used by refrigeration users; the ice machine I’m referring to is indeed one used in ice machine operations. The temperature is determined by the gas-phase pressure of the user’s heat exchanger. It would be great if our boss could see this statement, bro.
The temperature should be equivalent to the saturation temperature of liquid ammonia at 0.42 MPa, roughly 0℃