For engineering purposes, some useful values of caracteristic lengths and volumes may be obtained from the model. Neglecting the thickness of the moulded wave guide, the following table gives dimensional requirements for designing with a good accuracy a 1kw WR340 heat transfer with a liquid slab of thickness e = 5 mm.
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Table 1 Having chosen d = 0.99 with DT = 15 °C for a
minimum flow rate of water of 1 litre/mn and for a microwave
power of 1 kw, the minimum required length for a rectangular
liquid slab of thickness e = 5mm and height b
is approximately 30 cm. In the case of an inner pipe of height h(z) one will refer to the necessary volume of water V = 60 cubic cm which leads to the required ratio d = 0.99. The volume of water of 60 cubic cm is also valid for other values of e as this one is substantially smaller than the width of the heat transfer. These results show that the heat transfer become inconveniently long for higher microwave power. Thus for reasons of economy and conception, it is more advantageous to manufacture a modular system of 1 kw rather than 2, 4 or 6 kw. |
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