In a glass plant in Cavite, a furnace has fire-brick walls made up of the following two materials in series : Non-corrosive brick as inner layer (material 1) Clay brick as outer layer (material 2) Thickness 4.5 inches 8 inches Thermal conductivity k1 k2 The temperature inside the furnace (inside wall surface of the non-corrosive brick) is found to be 1105 oF while the outside temperature (outside wall surface of clay brick) is 365 oF. This is not the desired temperature inside the furnace so engineers thought of lagging the furnace walls with another material to reduce heat loss. The additional lagging material consists of magnesia layer which is 2 inches thick and has a thermal conductivity of 0.04 Btu /h.ft.oF. During a test run on the furnace with the magnesia lagging material now, new temperature readings were recorded : Point of measurement Temperature reading Inside furnace (inside wall surface of non-corrosive brick 1355 oF Interface between non-corrosive brick and clay brick 1290 oF Interface between clay brick and magnesia 890 oF Outside furnace (outside wall surface of magnesia) 190 oF With these new temperature readings, the engineers concluded that the magnesia lagging material has led to reduction in heat loss. How much was the % heat loss saved by the magnesia lagging ?
In a glass plant in Cavite, a furnace has fire-brick walls made up of the following two materials in series :
Non-corrosive brick as inner layer (material 1)
Clay brick as outer layer (material 2)
Thickness
4.5 inches
8 inches
Thermal conductivity
k1
k2
The temperature inside the furnace (inside wall surface of the non-corrosive brick) is found to be 1105 oF while the outside temperature (outside wall surface of clay brick) is 365 oF. This is not the desired temperature inside the furnace so engineers thought of lagging the furnace walls with another material to reduce heat loss. The additional lagging material consists of magnesia layer which is 2 inches thick and has a thermal conductivity of 0.04 Btu /h.ft.oF.
During a test run on the furnace with the magnesia lagging material now, new temperature readings were recorded :
Point of measurement
Temperature reading
Inside furnace (inside wall surface of non-corrosive brick
1355 oF
Interface between non-corrosive brick and clay brick
1290 oF
Interface between clay brick and magnesia
890 oF
Outside furnace (outside wall surface of magnesia)
190 oF
With these new temperature readings, the engineers concluded that the magnesia lagging material has led to reduction in heat loss. How much was the % heat loss saved by the magnesia lagging ?
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