Chapter 7 Heating and Heat Management

1. Chapter 7 Heating and Heat Management

2. How comfortable are you? • What temperature is comfortable? • How does humidity affect comfort?

3. Heat • Heat • Energy imparted into molecules • Heat Quantity • British thermal units (BTU) • Measurement in the US and a few other English-speaking countries • Watt: used throughout the rest of the world • Heat Quality • Temperature • Fahrenheit • This scale is the most common in both the United States and other English speaking nations • Celsius: used throughout the rest of the world

4. Products or Matter • Can exist in 1 of 3 energy states • Solid – lowest energy state, molecules closest together • Liquid • Gas – molecules furthest apart • Application • We can change from one state to another • This adds or removes heat energy • This heats or cools!

5. Heat and Temperature • Temperature • used to control heat input • controls heat energy costs

6. Types of Heat • Sensible heat • increases the product temperature with out bringing about change of state. • molecules vibrate faster as they absorb energy. • Measured with a thermometer. • Amount of change depends on • Thermal property • Specific heat • Weight • Latent heat • heat necessary to bring about change of state in a product (the product’s freezing or melting point). • Example: from a solid to a liquid. • Latent heat is a product critical temperature.

7. Heat Transfer • Definition: • Heat-energy moves from hot to cold • Varies by: • difference in temperatures • surface area • material conductivity • Ex: insulation lowers conductivity, slowing transfer • Transfer examples: • increase the heat transfer by cooking food • reduce the rate of heat transfer by slowing down the rate of heat loss from a building during winter.

8. Heat Transfer • 3 methods of heat transfer • Conduction • occurs within solids, or from one solid to another when the two • Requires direct contact • Thermal energy imparted to a molecule causes it to vibrate. This molecule vibrates against the second molecule and in turn the first molecule imparts energy to the second and a chain reaction develops. • Convection • this process involves the movement of heat between two bodies or surfaces • not in contact • separated by a fluid such as water, oil, air or steam • Radiation • heat that is transferred from a hot surface (body) to a cold surface (body) not in contact, by electromagnetic waves (equivalent to radio and television waves). • (in most cases all three methods occur at the same time)

9. Heat Transfer • Thermal Conductivity • Should be as low as possible • Measured in resistance (R-Value) • So you want a high r-value • Is more insulation better? • Considerations • Heating costs • Cooling costs • Insulation costs • Use of facility • Local weather conditions

10. Heat Transfer • U-Value • is the inverse of R-value • U = 1 / R • U-Value is the rate of heat flow • E-Value • Emissivity, or ability to block in windows • Ability to reflect

11. Insulation and Heat Transfer • Rate of building heat loss depends… • construction techniques and materials. • amount of thermal insulation. • in the past, low-cost heat resources did not usually provide economic incentives to add additional insulation. • older properties may be lacking. • currently, higher heating costs make costly insulation feasible investments. • Insulation • now universally accepted as an excellent energy-management tool and is vital in helping manage a building’s heating system.

12. Types of Heating Systems • By Energy Source • Gas • SNG, LPG, LNG • Oil • Coal • Steam • Electricity • Solar

13. Types of Heating Systems • By Process Method • Water • Hot water baseboards • Convectors • Radiant • In floors, walls, ceilings • Or, water heating forced air in a plenun Single pipe systems Double-pipe system

14. Types of Heating Systems • By Process Method • Steam • Radiators • Plenums heating forced air • Forced Air • Electric • Fireplaces • Gas Heaters

15. Managing Building Heating Systems • The costs within our control • Building construction and insulation; • Vital in designing a property • Specific to geographic location • Building temperature • Since the 1960s an average property keeps the inside temperature at 65 degrees F in the winter and 72 F in the summer.

16. Managing Building Heating Systems • The costs within our Control • Energy Selection • Determine future energy costs • Also consider environmental costs • There are three primary building heat fuels currently being used in most properties; • Oil, natural gas, and electricity. • Secondary building heat resources • used less frequently or in conjunction with primary fuels • steam, solar energy, LPG, and coal

17. Managing Building Heating Systems • Heating system selection factors: • Fuel availability • Fuel storage requirements • Heat recovery capabilities • Temperature and moisture quality • Fuel conservation efficiency • Pollution standards • System cost • Hazard potential and insurance • Availability of new systems • Employees skill requirements • Flexibility • Building code requirements • Fixed and variable system cost • usually related and must be analyzed by management when a heating system is selected.

18. Managing Heating Systems • Heat Control Networks • Thermostat • Most commonly used heat control network • Bimetallic or digital • Senses the temperature at its location • Compares this temperature to a specified temperature or setting • Computer heat system control • A computer controls each room’s temperature by the settings that are put in place but the management team. • Interfaces with property management system • Gaining popularity • Note: find your automatic shut-off valves.

19. Geothermal Heat Pump Systems http://geoheat.oit.edu/bulletin/bull28-2/art1.pdf