Short Interview Question Answers on Heat Exchangers–Parallel and counter flow, Duty of a heat exchanger, Plate heat exchanger and effectiveness, Explain when one fluid is undergoing phase change, the direction of flow is immaterial for finding LMTD , When will the outlet temperature of a cold fluid be higher than outlet temperature of a hot fluid in […]
Short Interview Question Answer on Heat Exchangers Q. What are multi-pass heat exchangers? When are these used? Multi-pass heat exchangers are of three types. 1. Multi-pass shell heat exchanger when fluid passes through more than one shell and the other fluid passes through a single tube pass, it is multi-shell pass heat exchanger. 2. Multi-tube pass heat […]
Heat Exchangers—4–Derivation of LMTD for a Counter Flow Heat Exchanger DERIVATION OF LMTD FOR COUNTER FLOW HEAT EXCHANGER Assumptions used 1. U is constant all along the HEX. 2. Steady flow conditions. 3. Specific heats of hot and cold fluids are constant 4. Flow rates of hot and cold fluids are constant. 5.There is no […]
Heat Exchangers, Mechanical Engineering–Analysis of Heat Exchangers ANALYSIS OF HEAT EXCHANGERS (a) LMTD METHOD (i) when all the four temperatures are known. q.=U A LMTD (ii) When fouling is to be considered q.=Udirty A LMTD where f=1/Udirty –1/Uclean Values of f and Uclean are given in standard tables. (i) ANALYSIS OF MULTIPASS HEAT EXCHANGERS For multipass shell/multipass […]
Heat Exchangers–3–Derivation of LMTD for a Parallel Flow Heat Exchanger DERIVATION FOR LOGARITHMIC MEAN TEMPERATURE DIFFERENCE ‘ LMTD ‘ FOR A PARALLEL FLOW HEAT EX-CHANGER It is an equivalent constant temperature difference in place of variable temperature difference in actual. It will give constant average rate of heat transfer. ASSUMPTIONS USED IN DERIVATION OF LMTD […]
*HEAT TRANSFER MECHANICAL ENGINEERING Heat Exchangers–2—U—Overall heat transfer Coefficient DEFINITION OF OVERALL HEAT TRANSFER COEFFICIENT ‘U’ Overall heat transfer coefficient for conduction and convection taking place simultaneously.Its units are W/m2 K. 1/UA =1/hiAi+fi + ln (r2/r1)/2πkL +1/hoAo + fo Where fi and fo are fouling resistances on the inner and outer surfaces. CALCULATION OF U (i) On the basis […]
Heat Exchangers, Mechanical Engineering—Introduction Definition of heat exchanger, definition of compact HEX, Types of HEX, Practical applications of HEX, Definition of U, Resistance of a HEX, Fouling in a HEX, How to account for Fouling, Methods of analysis for HEX, LMTD method, NTU method, Design equation for a Simple HEX, Design equation for a multi-pass […]