Abstract

An evaporative cooling system for the preservation of fresh vegetables was developed for extending the shelf life of tomatoes and carrots and its performance was evaluated. It consists of a pyramidal shaped with total storage space of 0.075 m³, made of galvanized mild steel, stainless steel and internally insulated with 0.025 m polystyrene foam, a suction fan of 4.3 m/s velocity air flow and 0.5 W (1250 rpm), cooling pad (Jute) of 0.06 m thickness and water pump with discharge capacity of 3.5 l/min as well as a power rating of 0.5 W. A water reservoir of capacity 62.5 m³ is linked to the cooling system at the bottom through a P.V.C. pipe supplying water to keep the cooling pad/mesh continuously wet. Study was conducted to check the freshness of tomatoes and carrots, and data were observed daily. Results of the transient performance tests revealed that the evaporative cooling system chamber temperature and relative humidity depression from ambient air temperature varied over 16-26°C and 33-88% respectively. Ambient air temperatures and relative humidity during the test periods ranged over 26-32°C and 18-31% respectively. The shelf life of the vegetable produce inside the evaporative cooling system was extended by fourteen days relative to ambient storage. Thus, the evaporative cooling system has the prospect of being used for short term preservation of vegetables soon after harvest and it will be very useful in a developing economy like Nigeria.

Key words: Evaporative cooling systems, fresh vegetables, preservation, modeling, temperature, relative humidity, tomatoes and carrots.