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Heating and Air Conditioning I

Heating and Air Conditioning I

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Heating and Air Conditioning I

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  1. Heating and Air Conditioning I Principles of Heating, Ventilating and Air Conditioning R.H. Howell, H.J. Sauer, and W.J. Coad ASHRAE, 2005 basic textbook/reference material For ME 421 John P. Renie Adjunct Professor – Spring 2009

  2. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology. • During winter months – sutained periods of cold with small variation. • Heat loss constant – peak during early morning – worst case scenario – in absence of solar effect and the presence of people, lighting, appliance. • Determine maximum heat loss of each room and space due to transmission and infiltration • Design condition based on worse case – set-back thermostat may require some excess capacity • Equations used given in Table 6-15

  3. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology.

  4. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – General Procedure

  5. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – General Procedure

  6. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – General Procedure

  7. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – General Procedure

  8. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – General Procedure • Conductive and convective heat transfer given by …

  9. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Heating Design Conditions • Ideal solution – maximum output capacity = most severe local weather conditions. Not economical – excess capacity for most of design life. • Questions to ask concerning outside design temperature • Type of structure? Heavy, medium, or light? • Is structure insulated? • Exposed to high winds? • More glass area than usual? • Nature of occupancy? • Long period of low temperature – non occupancy? • Daily temperature fluctuations? • Any other heating devices in building? • If design temperature difference is exceeded, the indoor temperature will fall – depends on thermal mass • Effect of wind should be considered – effects poorly insulated walls and windows – lend to more infiltration

  10. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Above Ground Exterior Surfaces • Above ground surface exposed to outdoor temperatures

  11. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Below-Grade Surfaces • Basement walls and floors depends on temperature between inside and ground, materials, conductivity of surrounding earth • Earth has time lag due to thermal inertia – not a steady state type of calculation – approximate method …

  12. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Below-Grade Surfaces

  13. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Below-Grade Surfaces

  14. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Below-Grade Surfaces • Thermal conductivity of ground varies widely dependent on the soil type and moisture content • Typically, k = 0.8 Btu/hr-ft-F – calculate R = 1.47 for uninsulated concrete walls

  15. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Below-Grade Surfaces

  16. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – On-Grade Surfaces • Concrete surface heated from above or within. Most loss occurs through the perimeter – proportional to the perimeter length • Simplified approach …

  17. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – On-Grade Surfaces

  18. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – On-Grade Surfaces

  19. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Buffer Spaces • Heat loss to adjacent unconditioned or semi-conditioned spaces based on partition temperature difference.

  20. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Infiltration Heat Loss • Divided into sensible and latent components • Energy to raise temperature up to indoor temperature is the sensible component • Energy quantity associated with the net loss of moisture from the space is the latent component. • Example 6-3

  21. Chapter 6 – Residential Cooling/Heating • Example 6-4

  22. Chapter 6 – Residential Cooling/Heating • Example 6-5

  23. Chapter 6 – Residential Cooling/Heating • Example 6-5

  24. Chapter 6 – Residential Cooling/Heating • Example 6-5

  25. Chapter 6 – Residential Cooling/Heating • Example 6-5

  26. Chapter 6 – Residential Cooling/Heating • Example 6-6

  27. Chapter 6 – Residential Cooling/Heating • Example 6-6

  28. Chapter 6 – Residential Cooling/Heating • Example 6-7

  29. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Heating Load Summary Sheet • For a multi-space building – see Figure 6-2

  30. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Heating Load Summary Sheet • For a multi-space building – see Figure 6-2

  31. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Heating Load Summary Sheet • Nomenclature

  32. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Heating Load Summary Sheet • Nomenclature

  33. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Heating Load Summary Sheet • Nomenclature

  34. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Heating Load Summary Sheet • Nomenclature

  35. Chapter 6 – Residential Cooling/Heating • Heating Load Methodology – Heating Load Summary Sheet • Nomenclature

  36. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • Floor plan

  37. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • House characteristics

  38. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • House characteristics

  39. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • Design Conditions

  40. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • Component Characteristics

  41. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • Opaque Surface Factors – Table 6-22

  42. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • Opaque Surface Factors – Table 6-22

  43. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • Window Factors – Table 6-23 • Note that some references are refering to equation numbers in Chapter 29 of the 2005 Fundamentals – I am trying to acquire this ASAP.

  44. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • Window Factors – example of 3 ft – west facing window

  45. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • Window Factors – example of 3 ft – west facing window

  46. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • Envelope Loads

  47. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • Infiltration and Ventilation • Procedure discussed in text • Table 6-3 for unit leakage, determine AL = 77 in2 • Heating and cooling IDF estimated

  48. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • Air changes per hour determined • Ventilation determined

  49. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • Determine sensible infiltration/ventilation loads

  50. Chapter 6 – Residential Cooling/Heating • Example Load Calculation … Atlanta Georgia Home • Internal Gains • Distribution Losses and Total Sensible Load