Influence of Airflow Field on Food Freezing and Energy Consumption in Cold Storage

Guohui Feng,Xiaohang Cheng,Guiqiang Wang,C.-H Weng,Zhiqiangè Kang,R Weerasinghe

doi:10.1051/e3sconf/20185301038

Abstract

Currently most food products are cooled and frozen in air-blast cold storage to prolong storage time. The airflow field distribution in storage has a great impact on the process of food freezing and energy cost by that. In this paper, a transient model of food freezing considering airflow field was developed to simulation the temperature profile of air and food products during freezing process. A lumped parameter model was used to predict the temperature and moisture profile of air, which connected all other components together, such as air coolers, food products, envelop enclosure and refrigeration system. A finite difference method was employed to model the heat transfer inside food products during freezing, where the mass transfer was neglected as the food products were wrapped with polystyrene films. Unit load factor method was applied to calculate the sensible heat refrigeration capacity and thus the total capacity of air coolers. The simulation was conducted on a large cold storage filled with large quantities of packaged food products. Results show that there are great differences in airflow field distribution at different locations in cold storage, which lead to spacial differences in freezing time required. Inappropriate set point of freezing time prolongs freezing process unnecessarily and leads to extra energy consumption. Operational mode of air coolers has a great impact on the total energy consumption, as they consume energy themselves and release equivalent heat into storage simultaneously.

Highlights

Freezing and cooling are widely used food preservation methods, and air-blast freezing is the most effective way due to the forced convection occurred between air and food products
Six air coolers were located at the top of cold storage, which drive air to circulate and carry away the heat released by food
Analysis shows that the set point of freezing time is too large for carton box packaged food, which prolongs the freezing process unnecessarily and reduces the food temperature much lower than the target point

Summary

Introduction

Freezing and cooling are widely used food preservation methods, and air-blast freezing is the most effective way due to the forced convection occurred between air and food products. Numerical methods constitute a promising way to simulate airflow field and the accuracy depends on accurate knowledge of thermal properties and mathematical models[1,2,3,4,5]. Chourasia studied the effect of the parameters of the product and the operating conditions on heat and mass transfer in the stack of bagged potatoes during the transient cooling and at steady state using the CFD modeling approach[13]. Most existing operation strategies of air-blast cold storage rely on the freezing time, which ensures that thermal center temperature of food is reduced to target point(-15°C or -18°C) in a limited period of time. The objective of the work is to simulate the food freezing process and incorporate airflow filed distribution to analyze the operation strategy and energy consumption

Models

Result and discussion

Conclusion