Theory of Heat Exchanging P M V Subbarao
Theory of Heat Exchanging P M V Subbarao Professor Mechanical Engineering Department I I T Delhi Understanding of Qualities of An Ideal Heat Exchangers…. .
Theoretical Base for Working of Heat Exchangers • A Simple adiabatic Heat Exchanger model. Hot fluid Cold fluid
Electrical Analogy of A Finite Heat Exchanger Hot fluid Cold fluid
Basic Information for Overall Resistance/Conductance
Heat Transfer between two fluids separated by finite thick surface wall
First Level Engineering Compromise: Area Energy Balance:
Second Level Engineering Compromise: DTeffective Mean Temperature Difference • A Simple adiabatic Heat Exchanger model.
Second Level Engineering Compromise: DT
Simple Counter Flow Heat Exchangers
Simple Counter Flow Heat Exchangers: C < 1
Simple Parallel Flow Heat Exchangers
Theoretical Base for Working of Heat Exchangers • A Simple adiabatic Heat Exchanger model. • For an Infinitesimal Heat communication between cold and hot.
Third Level Engineering Compromise: variation of U U
How many "zones" are involved in A HX?
Various Simple Zones (HX)
How many "zones" are involved in A HX? • "Zones" can best be defined as regimes of phase changes where the overall heat transfer coefficient (U) will vary. • Using T-Q (Temperature-Heat) diagrams are the best way to pinpoint zones. • The system is defined as co-current or countercurrent and the diagram is constructed. • The diagram on the left illustrates the use of T-Q diagrams. • These diagrams should accompany your basic (inputoutput) diagram of the heat exchanger. • Defining zones is one of the most important aspects of heat exchanger design.
Role of SG in Rankine Cycle
Gas to Phase Changing Fluid Heat Exchange Li qu id H ea tin g
Thermal Structure of A Boiler Furnace Platen SHTR drum DPNL R H T R screen tubes LTSH Economiser stack BCW pump Furnace APH Bottom ash ESP ID Fan
A Simple Heat Exchanger Annular Flow Tubular Flow di do Di Overall heat transfer coefficient of a used HX, based on outside area:
Overall heat transfer coefficient of a new/cleaned HX, based on outside area: Thermal resistance of any annular solid structure:
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