12 HEAT EXCHANGERS CHEMICAL ENGINEERING 170 REVIEW HEAT

12. HEAT EXCHANGERS CHEMICAL ENGINEERING 170

REVIEW: HEAT TRANSFER Explain the different mechanisms of heat transfer: Conduction Convection Radiation

REVIEW: ENERGY BALANCES Where would you use each equation?

HEAT EXCHANGERS In industrial settings, we transfer heat using a heat exchanger.

HEAT DUTY

FINDING HEAT DUTY In an oil refinery, an oil stream is heated to a higher temperature using a heat exchanger with steam being condensed to water as the heat source. You have complete information about both streams. Describe two different ways of finding the heat duty (two different equations you could use).

FINDING HEAT DUTY In an oil refinery, an oil stream is heated to a higher temperature using a heat exchanger with steam being condensed to water as the heat source. You have complete information about both streams. Describe two different ways of finding the heat duty (two different equations you could use). Oil (Cold Stream) Water (Hot Steam)

SIZING HEAT EXCHANGERS Overall heat transfer coefficient Heat transfer area Temperature difference between hot and cold streams (averaged)

TYPICAL UNITS ?

TYPICAL UNITS

AVERAGE TEMPERATURE DIFFERENCE Why do we need to average the temperature difference?

LOG MEAN TEMPERATURE DIFFERENCE For a simple heat exchanger (the only kind we’ll be using):

FINDING HEAT DUTY A chemical process creates a very hot waste stream. We will use a stream of cold water to cool it before it can be released. We have the following information about the two streams:

FINDING HEAT DUTY A chemical process creates a very hot waste stream. We will use a stream of cold water to cool it before it can be released. We have the following information about the two streams: Waste Stream (Hot) Cooling Water (Cold)