1. Objectives Heat exchangers Fluid mechanics (ducts and pitot tubes) Introduction to psychrometrics

2. Any Questions/Administrative Issues? Syllabus Website Homework Lecture notes/videos Feedback? Is no PDF okay?

3. Indoor Air 2005 Very successful and engaging conference Excellent talks and discussion Trends for the future Indoor secondary pollutants PCO (mixed feelings) Whole-building approaches/solutions Focus on lesser-developed nations

4. Photo Album

12. Heat Exchangers Counterflow Crossflow Cocurrent flow Ref: Incropera & Dewitt (2002)

13. Shell-and-Tube Heat Exchanger Ref: Incropera & Dewitt (2002)

14. Heat Exchanger Analysis

15. We want to know the energy exchange between two fluids But, the temperature difference is not constant Q = UAΔt m The trick is coming up with appropriate expression for Δ t m Q= heat transferred (W, BTU/hr) UA = area × U-value (W/K, Btu/hr/F) Δt m = mean temperature difference (°F, °C)

16. Heat Exchanger Analysis Counterflow Parallel

17. Fluid Flow in Pipes Analogy to steady-flow energy equation Consider incompressible, isothermal flow What is friction loss?

18. Pitot Tubes

19. Summary Use relationships in text to solve conduction, convection, radiation, phase change, and mixed-mode heat transfer problems Calculate components of pressure for flow in pipes and ducts

20. Any questions about review material? Where are we going? Psychrometrics Psychrometric terms Using tables for moist air Application of IGL Using psychrometric charts 7.1 – 7.5, 7.7

21. Humidity Ratio, W W = m w /m a Degree of saturation, µ = W/W s Humidity ratio is hard to measure, but very useful in calculations What are units? Is W a function of temperature? What about W s ? W s = humidity ratio at saturation m a = mass of dry air m w = mass of water vapor

22. Relative Humidity Φ = x w /x w,s = P w /P ws Function of T Easy to measure and useful in some contexts, but often need to know temperature as well x = mole fraction P = pressure μ = degree of saturation W = humidity ratio

23. Summary Review material in chapter 2 Describe psychrometric quantities