HVAC Engenering technical formula for Electrical and mechanical All Engineering Students Useful formula open now

Electrical and mechanical 
All Engineering Students Useful formula 

  1.  Length
  2. 1mtr = 3.28 ft 
  3. 1foot = 0.3048m or 304.8 mm
  4. 1 foot = 12 inches
  5. 1 inch = 25.4 mm
  6. 1 mtr  = 1000 mm
  7. 1 mtr  = 100 cm
  8. 1 cm  = 10 mm
  9. Area
  10. 1 m2   = (3.28 ft x 3.28 ft) = 10.76 ft2
  11. 1 ft2      = (1foot x 1foot) = (12 inch x 12 inch) = 144 inch2
  12. 1 m2      = (1000mm x 1000mm) = 10,000,000 mm2
  13. 1 m2      = (100cm x 100cm) = 10000 cm2
  14. Volume
  15. 1 m3   = (3.28 ft x 3.28 ft x 3.28 ft) = 35.28 ft3
  16. 1 m3 = 1000 litres
  17. 1 US gallon = 3.785 litres
  18. Mass 
  19. 1 kg  =  1000 
  20. gms
  21. 1 kg  =  2.2 Pounds or lbs
  22. 1 lb   = 7000 grains
  23. 1 Tonne = 1000 kgs
  24. 1 Tonne = 2200 lbs
  25.  Flow 
  26. 1 cfm = 1 ft3 / min = 1 x 60 x 1 / 35.28 = 1.7 m3 / h
  27. 1 cfm = 1.7 m3 / h = 1.7 x 1000/ 3600 secs = 0.4722 lps
  28. 1 lps  = 1/0.4722 = 2.12 cfm
  29. 1 lps  =  1 x (1/3.785)x60 = 15.85 US GPM
  30. Pressure
  31. 1 Bar = 1,00,000 Pa                                  Where Pa = Pascal
  32. 1 Bar = 1.02 kg/cm2 
  33. 1 mm of H2O = 9.81 Pa
  34. 1 mtr of H2O = 9810 Pa = 9.81 kPa
  35. 1 Atm = 101320 Pa = 101.320 kPa
  36. 1 Atm = 10.33m of H2O 
  37. 1 Atm = 760mm of Hg                          Where Hg = Mercury
  38. 1 Atm = 14.5 psi                                     Where psi = Pound force per square inch
  39. 1 psi    = 6895 Pa  = 6.895 kPa
  40. 1 psi    = 0.7 m of H2O
  41. Heat
  42. 1 BTU   = 1055 Joules                         where, BTU = British Thermal unit
  43. 1 calorie = 4.184 Joules
  44. 1 BTU   = 252 Calorie
  45. Heat transfer 
  46. 1 W              =  3.4 BTU / Hr                 where, W = Watt = Joule/s
  47. 1 kW            =  3400 BTU / Hr
  48. 1 k.Cal/Hr   =  3.97 BTU / Hr
  49. 1 TR        = 12000 BTU /Hr              where, TR = Tonne of Refrigeration    
  50. 1 TR              = 3.52 kW     
  51. U-value or Overall heat transfer co-efficient 
  52. 1 BTU/Hr.ft2.⁰F =  5.69 W/m2 ⁰k
  53. 1 W/m2 ⁰k       =   0.176  BTU/Hr.ft2.⁰F
  54. Temperature Conversion
  55. t⁰C  =   (t⁰F – 32) / 1.8      Degree Fahrenheit to Degree centigrade
  56. Example:1 Convert 96 ⁰F into ⁰C.
  57.  t⁰C  = (96-32)/1.8 = 35.55 ⁰C                
  58. t⁰F  = (t⁰C x 1.8) + 32       Degree centigrade to Degree Fahrenheit
  59. Example:2 Convert 23 ⁰C into ⁰F.
  60. t⁰F  = (23 x 1.8) + 32 = 73.4 ⁰F

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