Thermostatic Mixing Valves - Modeling and simulation of the thermostat under real operating conditions

摘要

The thermostat of a high performance thermostatic mixing valve (TMV) has been analyzed utilizing modeling and computer simulations. A model of a thermostat containing realistic boundary conditions obtained by a newly developed measurement method and material properties including the latent heat corresponding to a mixture of waxes inside the thermostat has been developed. By this approach, we focus on the thermostat as a system component, aiming at an increased understanding of how the overall performance of a TMV is affected by the thermal characteristics of the thermostat under real operating conditions. The obtained temperature-time characteristics show a relatively slow heating of the thermostat regardless of the flow rate. Substantial radial and axial temperature gradients and thus heat fluxes are present even several seconds after an imposed temperature step in the vicinity of the thermostat. This is an unexpected finding as the valve man ages to adopt to the changed conditions before the temperature distribution inside the thermostat has equilibrated.