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5/24/2013 1 Heat Transfer: transfer of energy from one object to another Direction: hot to cold British Thermal Unit (BTU): one degree of F per pound of water Calorie: one degree C per gram of water Three Methods: conduction, convection, radiation, Figure 11-1 Heat Transfer Coefficients: rate increase -- temperature difference -- surface area -- heat transfer coefficient 2 Other factors for heat transfer rate: -- fouling -- flow types Countercurrent flow, Figure 11-2 Co-current flow, Figure 11-3 Parallel flow: Figure 11-4 Cross flow: Figure 11-5 Flow Regimes: Laminar (streamline), Figure 11-6 Turbulent, Figure 11-7, baffles Reynolds number Types of Heat Exchangers Double-pipe, Figure 11-8 Spiral, Figure 11-9 Shell and Tube, Figure 11-10, 11-11 3 1 5/24/2013 Multi pass, Figure 11-12, 11-13 U-tube (hairpin), Figure 11-14 Plate and Frame: Figure 11-15 Components of Heat Exchanger, Figure 11-17 Tube bundle Shell Exchanger head Plain tubing, Figure 11-18 Tube sheet Exchanger Applications and Services Preheater Reboiler Condenser, Figure 11-19 4 Potential Problems: Deviations -- excessive pressure drop, loss of flow, lower of heat transfer, likelihood of fouling Safety and Environmental Hazards: Table 11-1, 11-2 Typical Procedures: Page 22--229 Startup Shutdown General Maintenance Tasks Backwashing (back-flushing) Technician’s Role: Table 11-3 5 2