Development And Application Of Composite Phase Change Refrigerant For Fresh Food

As cold chain foods develop rapidly.In order to solve the "last mile" problem of the Cold chain food develops rapidly.people use coolant extensively in transportation.However,the phase transition temperature is still not ideal,the latent heat of phase change is low,and there may be problems such as phase separation and supercooling.At present,there are few cold storage materials developed and applied.Therefore,this paper aims to study a new type of composite phase change coolant with higher phase change latent heat,more stable application state and higher economic benefit.Using(KCl)?(KNO3)?(Na2SO4)?(Na2CO3)?(C6H14O6)five materials as the main energy storage agent candidates for the cold storage,using differential scanning calorimetry(DSC)for different substances The phase change latent heat and phase transition temperature(Onset temperature)of the solution mass fraction were measured.It was found that the latent heat of phase change of each substance solution measured decreased with the increase of mass fraction,and the quality of the aqueous solution of the substance When the fraction is less than 2wt%,the latent heat of phase change of the five substances is above 310J/g.There is a certain fluctuation in the onset temperature of each substance,but the fluctuation range is small.The onset temperatures of Na2SO4,Na2CO3,KNO3,and C6H14O6 fluctuate within the temperature range of-1? to-5?,while the onset temperature of KCl is around-11?.The coolant selected in this paper has a target phase transition temperature range of-1? to-6?.The nitrate KNO3 with a mass fraction of 1wt%has the highest latent heat of phase change in this temperature range.Therefore,1wt%KNO3 is used as the main energy storage agent for the cold storage agent developed in this paper,and the inorganic substance Na2SO4 and organic matter C6H14O6 are used as additives to the cold storage agent.The main energy storage machine is compounded.By investigating the effect of the particle size of the superabsorbent resin on the water holding capacity,it was determined that the 400-mesh superabsorbent resin was used as a carrier and the phase separation preventing agent was used to improve the formulation.Through the single factor experimental design and the response surface optimization experiment,the optimal cold storage ratio of the onset temperature between-1? and-6? was obtained:KNO3 1wt%,Na2SO40.74wt%,SAP 0.88wt%,C6Hl4O6 0.75 wt%.The latent heat of phase change of the cold accumulator prepared by this formula was determined to be 331.06J/g and the phase transition temperature was-2.73?.Repeated freeze-thaw experiments were carried out on the optimal coolant formulation.The results show that there is no obvious phase separation and the phase change latent heat and phase transition temperature have no obvious change,and it has high stability.According to the literature and experiments,the commercial cold storage agent with the onset temperature in the temperature range of-1? to-6?.has a latent heat of phase change of about 290J/g.Compared with the commercially available coolant,the composite phase change coolant developed by the subject has higher latent heat of phase change and better low temperature retention ability.On this basis,this paper explores the practical application effect of cold storage agent,and selects three kinds of fresh foods such as mushroom,tomato and chicken breast as the experimental objects to simulate the cold storage,and compares with the application effect of the best commercial cold storage agent.By simulating the measurement data in the refrigeration,it can be obtained that the cold storage agent developed in this subject is superior to the commercially available cold storage agent in the low temperature maintenance;and the low temperature maintenance time has a certain relationship with the amount of the cold storage agent.The most suitable coolant-to-material ratio can be selected taking into account the time required for the transport scenario.However,materials such as chicken breast meat,which are mainly stored at the freezing temperature,cannot be guaranteed to be below-15?,which is required by the cold chain.Therefore,the cold accumulating agent developed in this project is used for materials stored at refrigerated temperature,and is not suitable for frozen temperature materials.Storage and transportation.In consideration of cost and economic benefits,the optimal material ratio of the cold storage agent to the ordinary fresh food product is 3:8,which has a better preservation effect and a longer holding time.At the same time,it is found that the use of too much cold storage will affect the economic benefits of storage,transportation and distribution.In the future research,we should find more efficient phase change coolant so that it does not take up too much space and increase excessive weight.