Plate heat exchanger temperature difference
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Question: In the internal compression process, what does the temperature difference between the high-pressure and low-pressure plate exchangers refer to – the difference between which two temperatures? How much to control? How to control it? 1. The forward-flowing gas at the high plate level comes from the extraction system at the pressure-boosting end of the expander; the air exiting the last stage of the expander constitutes the backflow gas, which includes low-pressure nitrogen, high-pressure liquid oxygen, and contaminated nitrogen. 2. The forward-flowing gas at the low plate level is air coming from the air compressor, while the backflow gas consists of contaminated nitrogen and low-pressure oxygen (with a trace amount of argon). Thank you all.
What I would like to ask is what is meant by the hot-end temperature difference and the cold-end temperature difference?
The temperature difference at the hot side of a high-pressure plate heat exchanger refers to the difference between the forward-flowing air (coming from the after-cooling stage of the booster and the after-cooling stage on the pressure-boosting side of the expander; this temperature difference is usually around 40 degrees) and the counter-flowing product gas (oxygen, contaminated nitrogen, nitrogen, etc.; this temperature difference is generally around 32–35 degrees). In the internal compression process, the temperature difference at the hot end of the high-pressure main heat exchanger is generally designed to be between 5 and 7 degrees.
The other end of the hot side is, of course, the cold side
The cold-side temperature difference of high-pressure plate exchangers refers to the temperature of the air exiting the plate where it is liquefied into liquid (usually between 99–105 K), as compared to the recirculating compressed liquid oxygen (typically around 92–95 K)； The temperature difference between the backflowing polluted nitrogen and nitrogen gas (usually around 97 K)
The answer above is very good; with further strict control. It can also be described as the temperature difference between two cold and hot fluids with similar pressures within the same heat exchanger. Controlling the temperature difference at the hot end is mainly due to the consideration of heat transfer efficiency under similar conditions during design, as explained in relevant materials
Thank you, I’m Kongfen, a beginner. Please give me some guidance.
The answers are all very professional; I’m not sure if they’re easy to understand. I think the difference in temperature for low-pressure conversion can be determined by the temperature difference between the polluted nitrogen gas and the low-pressure air. The temperature difference for high heat exchange can be determined by looking at the difference in temperature between the polluted nitrogen gas and the medium-pressure gas before they enter the heat exchanger; it is best to keep this difference within 3 degrees. Currently, it is 4-5 degrees. If the temperature difference is even greater, then the heat loss will be somewhat significant.