A counter flow heat exchanger is to heat air entering at $${400^ \circ }C$$ with a flow rate of $$6$$ $$kg/s$$ by the exhaust gas entering at $${800^ \circ }C$$ with a flow rate of $$4$$ $$kg/s$$. The overall heat transfer coefficient is $${100^ \circ }C$$ $$W/\left( {{m^2}K} \right)$$ and the outlet temperature of the air is $${551.5^ \circ }C.$$ Specific heat at constant pressure for both air and the exhaust gas can be taken as $$1100$$ $$J/(kgK).$$ Calculate the heat transfer area needed and the number of transfer units.

Two streams of fluid of unit constant specific heats and unit mass flow rate exchange thermal energy in an adiabatic heat exchanger. The inlet temps of hot and cold streams are $${300^ \circ }C$$ and $${30^ \circ }C$$ respectively. Calculate the $$LMTD$$ and effectiveness of the heat exchanger if the hot fluid is cooled to zero entropy condition.

A one shell pass, one tube-pass heat exchanger, has counter flow configuration between the shell side and tube side fluids. The total number of tubes within the heat exchanger is $$10$$ and the tube dimensions are $$ID=10$$ $$mm,$$ $$OD=12$$ $$mm$$ and length $$=1m.$$ saturated dry steam enters the shell side at a flow rate of $$2$$ $$kg/s$$ and the temp of $${100^ \circ }C.$$ In the tube side, cold water enters at a flow rate of $$10$$ $$kg/s$$ with an inlet temp of $${25^ \circ }C.$$ The $$OHTC$$ based on the outer surface area of the tubes is $$50$$ $$W/{m^2}K.$$ The specific heat of water is $$4.18$$ $$kJ/kg$$-$$K$$ and the latent heat of steam is $$2500$$ $$kJ/kg.$$ What is the condition of the steam at the exit.

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