1. 1 Heat Exchangers Industrial Air To Air

2. Exo has been providing heat recovery for 34 years Exo is a 30,000 square feet of production facility Quality system compliant with ISO-9001-2008 standards Exo Welders are American Welding Society qualified Exo has a Certified Weld Inspector on site 2

3. 1.Air to Air Heat Exchangers Are Used for… 2.Fundamentals of Heat Transfer 3.Basic Flow Patterns 4.Selection Criteria 5.Do’s and Don’ts 6.Exchanger Product Summary 7.Applications In This Presentation 3

4. Heat recovery o For preheating the same process o For another process o For combustion air pre-heating Isolate process from combustion air (Indirect heating) Oven/Furnace makeup air preheating Fume preheat on recuperative thermal oxidizers Secondary heat recovery on regenerative oxidizers Heat exchange and recovery for VOC concentrators Combustion air preheats CO 2 reductions 1 - Heat Exchangers Are Used for… 4

5. 2 - Fundamentals of Heat Transfer Combination of three heat transfer methods:  Convection (main driving force for the majority of exchangers)  Conduction (typically associated with connection points)  Radiation (widely used on very high temperature applications) 5

6. Heat Transfer Across a Plate Convective heat transfer of air to plate. Conductive heat transfer through plate. Convection zones are complicated by drag friction, slowing down the flows adjoining the plate. The result of drag is a pocket of air which insulates the plate (the boundary layer). Plate Hot Flow Cold Flow 6

7. Boundary Layer Insulating boundaries layers reduce heat exchanger efficiency. Increasing flow turbulence will “scrub” the boundary layers, reducing their thickness and thus improving heat transfer. Surface irregularities, velocity, tangential approaches all increase turbulence. (Note: “fouling” may also insulate the plate aside from the boundary layer; further reducing heat transfer). Boundary Layer Hot flowCold flowPlate T2T2 T1T1 Laminar Layer 7

8. Boundary Layer Turbulence Increases overall heat transfer by: Increasing flow velocity Pushing more volume through the exchanger Reducing the opening size Plate design Add surface features to interfere with the gas flow Change passageways to disturb laminar flows 8

9. Heat Transfer Effectiveness 1.Cannot transfer more heat than the hot stream can give 2.Cannot transfer more heat than the cold stream can receive 3.Amount transferred from hot stream must equal amount received by cold stream 9 Three basic fundamentals

10. t h,in & t h,out = Hot fluid temperatures t c,in & t c,out = Cold fluid temperatures C h = hot-fluid capacity rate C c = cold-fluid capacity rate C n = Btu/(hr °F), W/K or W/°C C min is the smaller of the C h and C c magnitudes Heat transfer is limited by the smaller capacity fluid Effectiveness (  ) 10

11. 3 – Basic Flow Patterns There are three common flow patterns for individual air-to-air heat exchangers: Counter Flow Parallel Flow Cross Flow 11

12. Counter Flow Hot flow and cold flow move in opposite directions along the length of the heat exchanger Outlet temperature of the cold flow can be hotter than the outlet temperature of the hot flow Most effective heat transfer arrangement Length Flow A Flow B Δt 1 Δt 2 t A1 t B1 t A2 t B2 Temperature 12 t A1 t B2 t A2 t B1

13. Parallel Flow Hot flow and cold flow move in the same direction along the length of the heat exchanger Outlet temperature of the cold flow can never be higher than the outlet temperature of the hot flow Flow A Flow B Δt 1 Δt 2 t A1 t B1 t A2 t B2 Temperature Length 13 t A1 t B1 t A2 t B2

14. Cross Flow Hot and cold flows run perpendicular to each other. Cross Flow heat exchangers may be designed for unequal flows more effectively than multi-pass designs Temperature profiles of flows leaving the unit are not uniform. ΔT 14

15. 4 – Selection Criteria Plate Exchanger Effectiveness typically over 45% (can be as high as 85%) Operating pressure under 3 PSI Temperatures under 1500ºF Minimal Particulate or condensable materials only Limited space requires compact unit Flow ratio under 2 or 3 to 1 Customer Preference Tubular Exchanger Effectiveness typically under 45% Higher Max Pressure Ratings Temperatures above 1500ºF Concern for Particulate Space not a problem Flow ratios 3 or 4 to 1 and above Customer Preference Plate Tube Run! 15

16. Choosing the optimum Heat Exchanger To arrive at the optimum heat exchanger solution we consider: 1.Problem specification 2.Surface characteristics 3.Physical properties 4.Design Theory 5.Optimal solutions 6.Evaluation Criteria 7.Evaluation Procedure 16

17. Choosing the optimum Heat Exchanger Questions that need answered before going through the steps 17 What are the targets? What are the limits? Water Vapor? Retrofit or new install? Corrosives or particulates?

18. 5 – Do’s and Don’ts Low, Moderate and High Temperatures Assuming a conventional high temperature alloy is applicable for use at 1700ºF to 1800ºF the exchanger needs to be designed to compensate for the higher thermal stresses or eliminate the stresses. An exchanger that operates… under 1200ºF is less subject to Sigma Phase under 600ºF is subject to far less expansion stress than at 1500ºF at or below 1100ºF is most likely further away from a catastrophic incident than one operating at 1600ºF at high temperature for 24/7 duty is less likely to see problems than a very cyclic operation 18

19. Excessive Metal Temperature Primary concern is related to exceeding the operational strength characteristics of the alloy being used. For simplicity we look at the arithmetic average of the temperatures on both sides of the Media at the hottest point to help avoid elevated temperature creep and other concerns. This comes in to play usually only when customers request high effectiveness with hot gas near design limit conditions. 19

20. Thermal Shock Treat an exchanger like you would like to be treated. Not too hot, not too cold (avoid extremes) Not too hot, too fast (heat up S-L-O-W-L-Y) Not too cold, too fast (don’t quench) Not hot and cold (they are not light switches) 20

21. Radiant Energy Exchangers dislike being licked by flames, they find it extremely uncomfortable. Exchangers tend to be pyro-phobic and prefer to remain out of sight. Having a 90 degree bend in a duct between any radiating chamber and exchanger or a heat shield is recommended. 21

22. 6 – Exchanger Product Summary Sinusoidal Plate stainless steel exchangers - 1200ºF (648ºC ) Dimpled Plate stainless steel exchangers - 1200ºF (648ºC) Alloy plate exchangers – Sinusoidal and Dimple (aluminum, exotic) Dimple plate insulated Recuperators - 1500ºF (815ºC) Tubular exchangers - 1600ºF (871ºC) Indirect Air Heat Systems – RHT and ER 22

23. Sinusoidal Plate vs. Dimpled Plate Sinusoidal  More compact of the two  Lower cost of the two  4, 6 and 8 foot units available  Less weight  Shorter lead times  Higher effectiveness, size for size Dimpled Width and height a concern Less compact, more costly Lengths up to 12 feet Thick plates for abrasive/corrosive applications Heavier weight In-line dimples accommodate dirtier streams Custom sizes 23

24. RHT Fully welded 309 stainless steel construction Designed to allow thermal expansion Low process air pressure drops Supplied with an Eclipse package burner, high temperature thermocouple and process air pressure switch Options for duct section, safety valve train, local junction box and control panel Burner options: RatioMatic, RatioAir & ThermAir Gross efficiencies up to 80% 24

25. Packaged Air Heaters RHT Air flows up to 28,000 scfm Temperature lifts of up to a maximum temperature of 550°F In-duct mounted heater with burner ER Heaters Air flows up to 100,000 scfm Temperature lifts of up to 600°F or better Package Heater with burner-remote or ducted 25

26. 7 – Applications: Combustion Air Pre-Heat Boiler Boiler Economizer To Atmosphere Fresh Air Pre-Heated Combustion Air Plate Heat Exchanger 26

27. 7 – Applications: Plant Make Up Air To Atmosphere Heater Fresh Air Warm Plant Make Up Air Plate Heat Exchanger 27

28. 7 – Applications: Pre-heated Process Air To Atmosphere Heater Plate Heat Exchanger Fresh Air To Process Boiler Economizer 28

29. 7 – Applications: Oxidizer Fume Pre-heat Cross Flow Tubular To Atmosphere Thermal Oxidizer Polluted Air Stream 29

30. 7 – Applications: Process Air Pre-Heat Process (eg. Potato Chip Fryer) To Atmosphere Thermal Oxidizer Fresh Air Pre-Heated Process Air Oil Return From Process Hot Oil To Process Polluted Air 30

31. Questions? - Thank You! 31 Please complete and turn in Today’s Appraisal Form