Insulating properties of styrofoam boxes used for transporting live fish

Abstract

Tropical fish are shown to be adapted to temperatures between 22–30°C and temperatures below 15–18°C are known to cause mortalities. Insulating properties of standard Styrofoam boxes used for shipping live fish were examined. The following equation can be used to estimate the change in water temperature over time in relation to box type, water volume/surface, water temperature and ambient temperature: T W e =T Air + T W b −T Air ·e − t·I·W s /W v , where T W e is the water temperature in degrees Celsius at the end of time interval t; T Air is the ambient air temperature; T W b is the water temperature at the beginning of time interval t; W S is the water surface in cm 2; and W V is the water volume in ml. I is the insulation coefficient and can be estimated as follows: I=W V·W −1 S · ln T db − ln T de ·t −1 , where T db is the difference in temperature between water and air at the beginning of time interval t, and T de is the difference in temperature between water and air at the end of the time interval. The average insulation coefficient for a standard Styrofoam box with 2.5 cm wall thickness and filled with about 8 ℓ water is I=0.11. The total surface area of the water in the box can be determined as follows: W S=2· B Li· B Wi+2· W V / B Wi+2· W V / B Li, where W S is the surface area in cm 2, B L i is the inner length and B W i is the inner width of the box in cm. Using thicker Styrofoam boxes or increasing insulation by other means is appropriate during Northern Hemisphere cold spells. Adding bags with hot water is less effective, but may be chosen when other means are not available. A better designed, cube-shaped Styrofoam box is suggested as the most promising and cost-effective measure to reduce mortalities resulting from heat loss during transport.