Chapter 7 Heatingand Heat Management Heat Management

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

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

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

Heat and Temperature Temperature Temperature used to control heat input used to control heat input controls heat energy costs controls heat energy costs

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

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

Heat Transfer 3 methods of heat transfer 3 methods of heat transfer Conduction Conduction occurs within solids, or from one solid to another when the two occurs within solids, or from one solid to another when the two Requires direct contact 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. 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 Convection this process involves the movement of heat between two bodies or surfaces this process involves the movement of heat between two bodies or surfaces not in contact not in contact separated by a fluid such as water, oil, air or steam separated by a fluid such as water, oil, air or steam Radiation 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). 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) (in most cases all three methods occur at the same time)

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

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

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

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

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

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

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

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

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

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

Geothermal Heat Pump Systems 2/art1.pdf