A note on energy saving in heated enclosures

When a closed space is heated, thermal stratification can be established such that the temperature at floor level is lower than that near the roof. There are two methods by which, during heating, the temperature at floor level can be raised to provide a convenient microclimate at the lower region. The first is by providing a surplus of heat to the space without destroying the thermal stratification, and the second is by mixing mechanically the air (while heating) to establish a uniform temperature distribution. A simple one-dimensional model is developed to calculate the energy required by each method. The results show that air mixing requires much less energy than surplus heating and is therefore a more economical method. In both methods, surplus heating and air mixing, the energy needed increases with the initial vertical temperature gradient existing in the heated enclosure and with the enclosure height.