Tanny, Josef, Cent for Technological Education, Holon, Holon, Israel
Teitel, Meir, Cent for Technological Education, Holon, Holon, Israel

When a closed space like a broiler budding or a greenhouse is heated, thermal stratification can be established. This stratification is usually undesirable since part of the heating energy is wasted in the unnecessary but unavoidable heating of the upper region. Therefore the temperature near the bottom has to be further raised to reach the desired level. This can be done in two ways. The first is by providing a surplus of heat without destroying the thermal stratification, and the second is by mixing mechanically the medium (while heating) to establish a uniform temperature distribution and hence to raise the bottom temperature. The objective of this study is to calculate the energy required by each way in an attempt to indicate the more economical one. The results of a theoretical one-dimensional model show that the ratio between the energies of mixing and surplus heating is very small, indicating that mixing is much more economical in raising the temperature of the lower region of the heated enclosure.