Why are HENs

Please find the highest thermal efficiency possible, while remaining within the boundaries.  What is required: -Power produced must be at least 60 Mega Watts -Thermal efficiency must be greater than 36% -Back-work ratio must be smaller than 48% Assume: -air is the working fluid -specific heats vary with temperature (use table A-17) -Compressor inlet is at 1atm and 300k -the combustion process is isobaric and is modeled as a heat exchanger -Turbine exhaust is the same pressure as compressor inlet Compressor specifics: -Max volume flow rate (m^3/h) = 600,000 -Max outlet pressure (atm) = 12 -Isentropic efficiency = 90% Combustion chamber and gas tubine specifics (Note these come as a set) -Max pressure = 16.7 atm -Max temp = 1500 (celcius) -Turbine isentropic efficiency = 92% -Max heat rate = 230MW

Homework: A counterflow heat exchanger is located between a collector and a storage tank. The fluid in the collector side is a water-glycol mixture with cp=3840 J/kg. °C and a flow rate of 1.35 kg/s, whereas the fluid in the tank side is water with a flow rate of 0.95 kg/s. If the UA of the heat exchanger is 5650 W/°C, the hot glycol enters the heat exchanger at 59°C, and the water from the tank at 39°C, a) estimate the heat exchange rate; b) if FRUL is 5.71 W/m².°C and collector area is 16 m², what is the ratio FR/FR?

A radiator heat exchanger is to be designed for the following specifications. Hot gas at 1145°C, Cold gas temperature 45°C, Unit surface conductance on the hot side, 230 W/m2-K, Unit surface conductance on the cold side 290 W/m2-K, Thermal conductivity of the metal wall 1115 W/m-K. Find the maximum thickness (in mm) of the metal wall between the hot gas and the cold gas so that the maximum temperature of the wall does not exceed 545°C.

1. In a shell and tube heat exchanger _________________________ a.The relationship between temperature drop and resistance is not generalized b.There is no relationship between temperature drop and resistance c.The temperature drop is inversely proportional to the resistance across which the drop occurs. d.the temperature drops in the two fluids and the wall are proportional to individual resistances