THERMAL COMFORT

THERMAL COMFORT Perception of temperature influenced by: Season Clothing Humidity Air Movement Presence of heat given off by other bodies and equipment

THERMAL COMFORT Body temperature regulated through: Skin Clothing Buildings www.adinstruments.com

THERMAL COMFORT Normal Body Temperature: 98.6 degrees Fahrenheit Few degree variation = distress www.fnal.gov

THERMAL COMFORT Between 1920 and 1970, a period of cheap energy costs, people developed a preference for year round temperatures in the range of 72 – 78 degrees Fahrenheit Preferred comfortable temperature for most people is 65 – 76 degrees Fahrenheit in the winter

THERMAL COMFORT Cold Sensitive Areas: Upper Lip Nose Chin Chest Fingertips

THERMAL COMFORT Thermal comfort is achieved when a stable, normal body temperature is achieved The result of a balance between the body and its environment

MAINTAINING THERMAL EQUILIBRIUM …when heat production equals heat loss

Building Heating and Cooling Systems: THERMAL COMFORT Building Heating and Cooling Systems: Used to control how much heat the human body gives off Does not heat/cool the body but adjust the thermal characteristics of the indoor space to reduce the rate at which our bodies lose heat

THERMAL COMFORT Gender Differences Men feel warmer than women when first in a space, but later feel cooler than a woman would Men take 1 – 2 hours to feel as warm/cool as a female in the same space

THERMAL COMFORT Age Differences Elderly and college age students are similar in the responses to thermal preferences and responses

THERMAL COMFORT Comfort Conditions Independent of the time of day or night Individuals are consistent in their thermal preferences www.iqdrive.net

THERMAL COMFORT ASHRAE Standard 55-1992: Thermal Environmental Conditions for Human Occupancy Describes the combinations of indoor space conditions and personal factors that create comfort

THERMAL COMFORT ASHRAE Standard 55-1992: Thermal Environmental Conditions for Human Occupancy Report indicates that our sense of being warm or cool enough is the result of interactions between: Temperature Thermal Radiation Humidity Air Speed Personal Activity Level Clothing

THERMAL COMFORT Thermal Sensations – feelings of being: Hot Warm Cool Cold Range of classifications in-between

THERMAL COMFORT Indices/Indexes – Integrate environmental factors used to describe thermal comfort conditions Dry-Bulb Temperatures Wet-Bulb Temperatures Operative Temperature

THERMAL COMFORT Dry-Bulb Temperatures The ambient air temperature as measured by a standard thermometer Wet-Bulb Temperatures Estimate the effect of temperature, humidity, wind speed and radiation

THERMAL COMFORT Operative Temperature Uniform temperature of an imaginary enclosure in which the occupant would exchange the same heat by radiation and convection as in the actual environment

Source: Bradshaw. The Building Environment. Wiley THERMAL COMFORT Effective Temperature Scale Correlated to Physiological Reactions, Comfort and Health Source: Bradshaw. The Building Environment. Wiley

Source: Bradshaw. The Building Environment. Wiley THERMAL COMFORT Guidelines for Room Air Temperatures Source: Bradshaw. The Building Environment. Wiley

THERMAL COMFORT Principles of Heat Transfer Heat always moves from the region of higher temperature to the region of lower temperature Heat flows from an area of active molecular movement to an area of less movement www.keltechnologies.com

THERMAL COMFORT Principles of Heat Transfer Tendency to decrease the temperature and amount of activity in the area with the higher temperature, and increase the temperature and activity in the area with the lowest temperature When there is no difference = Thermal Equilibrium

THERMAL COMFORT Principles of Heat Transfer Heat energy transferred by: Radiation Conduction Convection beyondpenguins.ehe.osu.edu www.physics.smu.edu

THERMAL COMFORT Principles of Heat Transfer Heat energy transferred by: Radiation Conduction Convection

THERMAL COMFORT Principles of Heat Transfer Radiation Occurs when heat flows in electromagnetic waves from hotter surfaces through any medium to detached colder surfaces

THERMAL COMFORT Principles of Heat Transfer Radiation Infrared electromagnetic waves emanate from an object and carry energy to all bodies within a direct line of sight of that object

THERMAL COMFORT Principles of Heat Transfer Radiation Electromagnetic waves excite the molecules in the objects they hit, increasing the internal energy, and raising the temperature

THERMAL COMFORT Principles of Heat Transfer Radiation: How building materials radiate heat Reflectance Absorptance Emittance

THERMAL COMFORT Principles of Heat Transfer Radiation: How building materials radiate heat Reflectance Absorptance Emittance Amount of incoming radiation that bounces off a material, leaving the temperature of the material unchanged White paint

THERMAL COMFORT

THERMAL COMFORT Principles of Heat Transfer Radiation: How building materials radiate heat Reflectance Absorptance Emittance Opposite of reflectance Allows thermal energy to enter, raising the temperature Stone

THERMAL COMFORT

THERMAL COMFORT Principles of Heat Transfer Radiation: How building materials radiate heat Reflectance Absorptance Emittance Ability of a material to radiate absorbed heat outward Black surfaces, stone

THERMAL COMFORT

THERMAL COMFORT Principles of Heat Transfer Radiation: Mean Radiant Temperature Air temperature alone does not adequately measure comfort in a space Engineers use a calculation called the Mean Radiant Temperature (MRT) Calculation takes into account heat emitted from surfaces etc

THERMAL COMFORT

THERMAL COMFORT Principles of Heat Transfer Radiation: Operative Temperature Physical measurement Average of the air temperature of a space and the average of the various surface temperatures surrounding the space

THERMAL COMFORT Principles of Heat Transfer Radiation: Mean Radiant Temperature and Operative Temperature are used by engineers to determine the amount of supplementary heating/cooling needed in a space

THERMAL COMFORT Principles of Heat Transfer Conduction Flow of heat through a solid material Represents a small fraction of heat loss from our bodies

THERMAL COMFORT Principles of Heat Transfer Convection Transfer of heat by means of a moving stream of a fluid (liquid or gas) rather than another object Air movement, water

THERMAL COMFORT Principles of Heat Transfer Evaporation Process that results from the three types of heat transfer Incorporates both sensible and latent heat

THERMAL COMFORT Principles of Heat Transfer Evaporation: Sensible Heat Created by the motion of molecules Latent Heat Heat that is transferred when a material changes from a solid to a liquid, or liquid to a gas form

THERMAL COMFORT Principles of Heat Transfer Evaporation: Evaporative Cooling Occurs when moisture evaporates and the sensible heat of the liquid is converted into the latent heat in the vapor Air movement increases heat loss caused by evaporation

THERMAL COMFORT muellerdesignlab.wordpress.com

THERMAL COMFORT Principles of Heat Transfer Air Temperature and Air Motion Natural convection of air over the body dissipates body heat without added air movement When temperatures rise – air movement must be increased to maintain thermal comfort

THERMAL COMFORT Principles of Heat Transfer Air Temperature and Relative Humidity (RH) Ratio of the amount of water vapor actually present in the air to the maximum amount that air could hold at the same time

THERMAL COMFORT Ted Talk http://www.ted.com/talks/wolfgang_kessling_how_to_air_condition_outdoor_spaces.html