| 摘要 |
PROBLEM TO BE SOLVED: To reduce the amount of a low temperature liquid required for refrigeration by a method wherein vapor formed by vaporizing a low temperature liquid is indirectly heat exchanged with a product to be refrigerated to heat the vapor, the vapor is expanded under loads, and the vapor obtained is then used to refrigerate the product. SOLUTION: In the device, a pump 11 is provided to take out a liquid nitrogen of -196 deg.C from a low temperature vessel 10 to deliver it at about 1.4 MPa. The liquid nitrogen is passed through a heat exchanger 12 so as to be vaporized. The nitrogen vapor is then used to cool a food 13 conveyed by a conveyor 14 passing through a refrigeration tunnel 15. The nitrogen vapor leaves the exchanger 12 at a temperature of about -40 deg.C and is passed through a work expansion instrument 16 under loads until the pressure thereof becomes atmospheric pressure. The cold nitrogen vapor leaving the instrument 16 is sent to the tunnel 15 to directly cool the food 13, and the nitrogen is vented from the tunnel 15 to the atmosphere through an exhaust duct 17. According to a result of calculation, consumption of liquid nitrogen for the tunnel can be decreased by about 25% as compared to a conventional tunnel.
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