Abstract: Abstract：Demanding for quick-frozen food and its quality in modern life, the requirements for food quick-freezingtechnology become challenging.The impingement quick-freezing equipment has drawn much attention in the most advancedquick-freezing technologies. The appropriate low-temperature flow field in the heat exchange zone of impingement quickfreezing equipment can reduce the time of food quick-freezing, while improve the quality of quick-frozen food. This paperaims to investigate the effect of air supply velocity on the freezing process of a single shrimp at the up and down within thechamber of impingement quick freezing equipment, using the numerical simulation and experimental verification. A singleshrimp was selected as the research object. The main purpose of this research wasto find the air supply conditions, which canshorten the freezing time of shrimp, and achieve the optimal flow field in the heat transfer area of the equipment. Threeexperimental groups were divided into: 1) the air supply velocity at the upper and downsides were kept the same and changedat the same time, 2) the air supply velocity of the upside was 15 m/s, while the downside was from zero to15 m/s, and 3) theair supply velocityon the downside was 15 m/s, while that on the upside was from zero to15 m/s. The results showed that thefreezing time of the shrimp shortened, but the gradient of decrease also reduced, as the increase of air supply velocity, whenthe air supply velocity was the same on both sides of the up and down impingement quick-freezing equipment. When the airsupply velocity on the upside was 15 m/s and the air supply velocity on the downside was from zero to four m/s, the relativeimpact of the two impinging jets can form an eddy current on the low velocity side, to promote the flow field on the surface ofshrimp, and improve the heat transfer efficiency of shrimp. When the air supply velocity of the downside exceeds 4 m/s, therelative impact of the two impinging jets can form a jet vacuum zone with down velocity on the surface of shrimp, reduced theheat transfer efficiency of shrimp. With the continuous increase of the downside air supply velocity, this adverse effect firstincreased and then decreased, the maximum appearedwhen the upside air supply velocity was 15 m/s and the downside airsupply velocity was eight m/s, and the frozen time of shrimp was the longest, which was 909 seconds. By the same token, whenthe downside air supply velocity was 15 m/s and the upside air supply velocity was from zero to two m/s, the relative impact ofthe two impinging jets can form an eddy current on the low velocity side, improve the heat transfer efficiency of shrimp. Whenthe air supply velocity of the upside exceeded two m/s, the relative impact of the two impinging jets can form a jet vacuumzone with down velocity on the surface of shrimp, reduced the heat transfer efficiency of shrimp. With the continuous increaseof the upside air supply velocity, this adverse effect first increasedand then decreased, it had a maximum when the downside airsupply velocity was 15 m/s and the upside air supply velocity was 5 m/s, and the frozen time of shrimp was the longest, whichwas 920 seconds. In the experimental range of impinging jet velocity, when the air supply velocity at the upside was 15 m/s andthe air velocity of the downside was 2 m/s, the freezing time of shrimp was the shortest, which was 617seconds.It inferedthatthe influence of the upper impinging jet on the freezing process was greater than that of the down impinging jet on the freezingprocess in the upper and down impingement quick-freezing equipment. Therefore, the upper impinging jet can play a leadingrole in the impingement quick-freezing equipment. The finding can provide an insightful reference to design the promisingoperating conditions for the up and down impingement quick-freezing equipment.