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Mechanical and HVAC systems For Construction

THINGS TO MAKE AND DO A Discussion of Temperature Scales A Bit of Thermodynamics The British Thermal Unit Heating Systems and Civilization Heat Loss Calculations Various Heating Systems Back to the RFI. Mechanical and HVAC systems For Construction. Heating.

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Mechanical and HVAC systems For Construction

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  1. THINGS TO MAKE AND DO A Discussion of Temperature Scales A Bit of Thermodynamics The British Thermal Unit Heating Systems and Civilization Heat Loss Calculations Various Heating Systems Back to the RFI Mechanical and HVAC systems For Construction Heating

  2. Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit (1686–1736). He defined the zero point by placing his thermometer in a brine of ice, water, and ammonium chloride. The second point, 100 degrees, was the level of the liquid in his thermometer when he held it in the mouth or under the armpit of his wife. Mechanical and HVAC systems For Construction °F Heating

  3. Celsius is the temperature scale named after the Swedish astronomer Anders Celsius (1701–1744). From 1744 until 1954, 0 °C was defined as the freezing point of water and 100 °C was defined as the boiling point of water, both at a pressure of one standard atmosphere. °C Mechanical And HVAC Systems For Construction Heating

  4. Converting from Fahrenheit to Celsius: °C = (°F − 32) x 5⁄9 Converting from Celsius to Fahrenheit: °F = (°C x 9⁄5 ) + 32 Kelvin K = (°F + 459.67) x 5⁄9 Rankine °R = °F + 459.67 Mechanical And HVAC Systems For Construction Heating

  5. William Thomson, 1st Baron Kelvin, (1824 – 1907) - Irish physicist and engineer. Lord Kelvin realized that there was a lower limit to temperature -- absolute zero; and absolute temperatures are stated in kelvins in his honor. He also formulated the First and Second Laws of Thermodynamics. Mechanical And HVAC Systems For Construction Heating

  6. Laws of Thermodynamics First You can’t create or destroy energy. You can only change its forms. Second Heat flows from hot things to colder ones, but not the other way around. Third The colder things get, the less energy is available for useful work. At absolute zero nothing gets done. Mechanical And HVAC Systems For Construction Heating

  7. BRITISH THERMAL UNIT The British Thermal Unit (BTU or Btu) is approximately the amount of energy needed to heat 1 pound of water 1 °F. Mechanical And HVAC Systems For Construction Heating

  8. So, if we have a pint of water at room temp (say 72 oF) and we want to cool it to 34 oF The temperature change is 38 oF and, at 1 degree F per btu/per pound, that means 38 btus need to be transferred. Going the other way, you need 38 btus to heat one pound of water from 72 oF to 110oF. If you want to get below 32oF or above 212 oF in that pint of water, other processes are involved. Mechanical And HVAC Systems For Construction Heating

  9. Calorie Calorie The Kilogram Calorie, Large Calorie, Food Calorie, Calorie (Capital C) Or Just Calorie (Lowercase C) Is The Amount Of Energy Required To Raise The Temperature Of One Kilogram Of Water By One Degree Celsius or Centigrade if you use the old units. 1 Kcal = 4186.8 J = 426.9 Kp.M = 1.163 10-3 Kwh = 3.088 Ft.Lbf = 3.9683 Btu = 1000 Cal Mechanical And HVAC Systems For Construction Heating

  10. Early Heating Systems Mechanical And HVAC Systems For Construction Heating

  11. The need for heat has affected architecture and human society for tens of thousands of years Mechanical And HVAC Systems For Construction Heating

  12. Heating systems did become a bit more sophisticated based as the materials and construction techniques available changed Mechanical And HVAC Systems For Construction Roman Hypocaust Heating

  13. but still, basically, heating systems involved an open fire Mechanical And HVAC Systems For Construction Heating

  14. Rumford (1735) and Franklin (1741) Mechanical And HVAC Systems For Construction Heating

  15. Unless you have access to an atomic power plant, a wind farm, a field of solar panels or a water fall Mechanical And HVAC Systems For Construction Heating

  16. you’ll end up burning something. Mechanical And HVAC Systems For Construction Heating

  17. Mechanical And HVAC Systems For Construction Heating

  18. From the 1990 census Natural (piped) or bottled gas was used to heat 57 percent of the housing units in the United States. Electricity was the main source of heat in 26 percent of housing units. About 12 percent of residences used fuel oil 4 percent used wood, coal, or solar energy. Only 1 percent of housing units used other types of fuels or did not use fuel at all. Mechanical And HVAC Systems For Construction Heating

  19. Heat Loss Calculation Mechanical And HVAC Systems For Construction Heating

  20. “U” Factors and “R” Values The “U-factor” is a measure of heat flow or conductivity through a material, the reciprocal of “R-value.” The “R-value” is a measures of the resistance to heat flow for individual building materials, “U” = 1/(R1 +R2+…+Rn) in Btuh / ft2 / oF Mechanical And HVAC Systems For Construction Heating

  21. Transmission Heat Loss Calculation Element “R” Outside Surface 0.17 Lapped Siding 0.81 Sheathing 4.00 Batt Insulation 13.00 Wall Board 0.45 Inside Air Film 0.68 Total Resistance 19.11 “R” = ft2x °F x hr / Btu “U” = 1/”R” = 0.0524 Btuh / ft2 / oF Mechanical And HVAC Systems For Construction Heating

  22. Mechanical And HVAC Systems For Construction Heating

  23. Transmission Heat Loss Calculation “U” = 1/”R” = 0.0524 Btuh / ft2 / oF “Q” = “U” x Area x Temp Difference Say 75 oF inside and 25 oF outside and a 10 Ft x 20 Ft wall “Q” = .0524 x 10 x 20 x (75 -25) = 545 Btuh loss Mechanical And HVAC Systems For Construction Heating

  24. Transmission Heat Loss Calculation From ASHRAE tabular data ; “U” for a double pane insulating window , 1/4” air space, 80% glass is 2.97 Btuh / ft2 / oF Say 75 oF inside and 25 oF outside and 3’ x 5’ Ftwindow “Q” = “U” x Area x Temp Difference “Q” = 2.97 x 3 x 5 x (75-25) = = 2228 Btuh loss Mechanical And HVAC Systems For Construction Heating

  25. Ventilation Heat Calculation “Q” = 1.08 x CFM x Temp Diff 0.24 btuh/lb/oF = Specific Heat of Air 60 min/hr 0.075 lb/ft3 1.08 btuh/ft3/min to heat or cool air say 100 CFM at 50oF Temp Diff “Q” = 5400 btuh loss Mechanical And HVAC Systems For Construction Heating

  26. Building Heat Loss Infrared Thermographic Imaging Mechanical And HVAC Systems For Construction Heating

  27. Building Heat Loss Thermal Bridging Mechanical And HVAC Systems For Construction Heating

  28. Building Heat Loss Calculation • The Building heating calculation is: One, • a tabulation of all of the surfaces where there’s a temperature difference, • & • calculations of the transmission heat loss, based on the “U” factors and temp differences Mechanical And HVAC Systems For Construction Heating

  29. Building Heat Loss Calculation • And Two, • a determination of what ventilation is required, and what infiltration is expected • & • calculations of the ventilation heat required based on the air flow and temp difference Mechanical And HVAC Systems For Construction Heating

  30. Building Heating Systems • Gas/Oil Forced Air Other Approaches • Direct Fired Wood/Coal Furnaces • In-Direct Fired Solar • Infra-Red Radiant Passive Solar • Electric Heat Recovery • Infra-Red Radiant Geo-Thermal • Radiant Floors • Air Coils Steam • Hot Water • Air Coils (“Heat Pumps“are air - • Radiators/Convectors conditioning units) Mechanical And HVAC Systems For Construction Heating

  31. Building Heating Systems Direct fired fuel systems with gas or oil burners in the air stream Mechanical And HVAC Systems For Construction Heating

  32. Building Heating Systems In-direct fired fuel systems with gas or oil burners separated from the air stream Mechanical And HVAC Systems For Construction Heating

  33. Building Heating Systems In-direct fired fuel systems require combustion air per FBC Mech Chapter 7. The requirements vary by system choice, but include wording and diagrams like this for each one. “The minimum required volume shall be 50 cubic feet per 1,000 Btu/h of the appliance input rating.” (there are exceptions) ‘Two permanent openings, one within 12 inches of the top and one within 12 inches of the bottom of the enclosure, shall be provided. Each opening shall have a minimum free area of 1 square inch per 4,000 Btu/h of total input rating of all appliances in the enclosure.’ Mechanical And HVAC Systems For Construction Heating

  34. Building Heating Systems The Mechanical Code also references The Fuel Gas Code for venting and gas piping design requirements for indirect fired equipment. High Pressure Pipe Sizing Low Pressure Pipe Sizing B-Vents are a Double Wall Gas Vent system listed to UL 441 and ULC S-605 and feature an Aluminum inner liner and Galvanized outer casing. The intent is to insulate the vent to prevent condensation in the vents. Mechanical And HVAC Systems For Construction Heating

  35. Building Heating Systems Gas Fired Radiant Heats with Infra-red energy radiated from the heater to the heated surface Does not heat the air Frequently used in manufacturing areas and shops. Mechanical And HVAC Systems For Construction Heating

  36. Building Heating Systems Gas Fired Radiant If you’re in the shadow , you’re not being heated. The further you are from the heater, the less effective it will be. The temperatures necessary can cause conduction and convection losses into spaces the heaters aren’t supposed to be heating. Combustion efficiency of radiant heaters is in the 60-70 percent range. The reflectors are affected by dirt and maintenance can become a factor. Mechanical And HVAC Systems For Construction Heating

  37. Building Heating Systems Hot Water Mechanical And HVAC Systems For Construction Heating

  38. Building Heating Systems Steam While It takes 212 btus to raise one pound of water from 0 oFto 212 oF it takes 1000 more btus to turn that pound into 1 pound of steam at 212 oF This is the LATENT HEAT OF VAPORIZATION Mechanical And HVAC Systems For Construction Heating

  39. Building Heating Systems Electric Heat The relationship between the current through a resistance and the heat dissipated, now called Joule's law, is named for James Prescott Joule. He worked with Lord Kelvin to develop the absolute scale of temperature. The SI derived unit of energy, the joule, is named after him. He found that the heat produced in an electrical circuit was proportional to the square of the current multiplied by the electrical resistance of the wire. This relationship is known as Joule's First Law. Q aI2x R Mechanical And HVAC Systems For Construction Heating

  40. Building Heating Systems Electric Heat is generally rated in Watts and Kilowatts. James Watt, 1736 – 1819 Scottish mechanical engineer whose improvements to the Newcomen steam engine aided the Industrial Revolution. He developed the concept of horsepower and invented a copying machine in 1794. 1 Watt = 1 Joule/Second 1000 Watts = 1 Kw 1 Kw = 3412 Buth Mechanical And HVAC Systems For Construction Dampfmaschine Heating

  41. Building Heating Systems Electric Radiant Same concept, different heat source. Mechanical And HVAC Systems For Construction Heating Heating

  42. Building Heating Systems Electric Radiant Flooring Mechanical And HVAC Systems For Construction Heating

  43. Building Heating Systems Electric Baseboard Heat Mechanical And HVAC Systems For Construction

  44. Building Heating Systems Electric Unit Heaters Mechanical And HVAC Systems For Construction Heating

  45. Building Heating Systems Electric Duct Heaters Mechanical And HVAC Systems For Construction Heating

  46. Building Heating Systems Electric Duct Heaters Mechanical And HVAC Systems For Construction Heating

  47. Building Heating Systems Electric Duct Heaters Mechanical And HVAC Systems For Construction Heating

  48. Building Heating Systems Electric Duct Heaters Mechanical And HVAC Systems For Construction Heating

  49. Building Heating Systems Electric Duct Heaters Mechanical And HVAC Systems For Construction Heating

  50. Building Heating Systems Electric Duct Heaters ASHRAE Guide Outdoor Air Temp 12 oF Design Low Temp Chosen 10oF (An arbitrary choice by the Engineer) Design Delivery Temp Chosen 60oF (This is a "tempering" system and is not intended for building heating.) Air Flow Required 900 Ft3/Min (CFM) Heat Required 900 CFM x [60-10] Deg F x 1.08 Btuh / CFM / Deg F = 48600 Btuh = 48600 Btuh/ 3412 Btuh/ Kw = 14.25 Kw Safety Factor 10 % = 14.25 Kw x 10 % = 15.675 Kw Mechanical And HVAC Systems For Construction Heating

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