A double pipe counter flow heat exchanger is to be designed to cool $$12000$$ $$kg/hr$$ of an oil of specific heat $$1.95$$ $$kJ/kgK$$ from $$\,85{}^ \circ C$$ to $$\,55{}^ \circ C$$ by water entering the heat exchanger at $$\,30{}^ \circ C$$ and leaving at $$\,45{}^ \circ C$$. If the $$OHTC$$ of heat exchanger is $$400$$ $$\,W/{m^2}K.\,$$ Calculate the $$LMTD$$ and the surface area of the heat exchanger

In pool boiling the highest $$HTC$$ occurs in

An iron rod $$\left( {K = 41.5W/mK} \right)$$ of $$15mm$$ diameter and $$160mm$$ long extends out of a hot surface of temp $${150^ \circ }C$$ into environment at $${36^ \circ }C.$$The free end of the rod is insulated. If the film heat transfer coefficient is $$25W/{m^2}K,$$ calculate the rate of heat flowing out of the hot surface through the rod and the temp at the insulated end of the rod.

Thermal conductivity is lower for