HEAT LOSSES THROUGH POLYURETHANE VALVE INSULATION

In our paper we tried to remind that valves are important sources of heat losses. An idea of valve insulation is presented. Calculations of heat losses were made for three different geometrical shapes: the cylinder, the sphere and the barrel. Heat flow can be easily analytically determined only in case of the hollow sphere. For a both-side-closed and short cylinder a solution exists but it is not simple and it is retardatory for repeated calculations. Because of the complex geometry boundary element method was used. Rigid polyurethane foam was used as the insulation material. We considered periodical (sinusoidal) change of the temperature of hot water which flows through the valve. Heat transfer model for this situation was made.
On the basis of the obtained results we determined economical thickness of the valve insulation. The graphical method was used. Influence of convection coefficient as well the temperature difference between hot fluid and ambient air on heat losses was determined.
From the results we get the most appropriate insulation jacket shape. It is also shown how much heat energy can be saved with proper insulation of the valves.