House ConstructionMike Riley & Alison Cotgrave3.3 The definition of thermal massThe term of thermal mass is to compare the ability of materials about absorb, store and release heat. A common comparation of the thermal mass is kind of thermal battery. The battery charged up by radiation or warmer adjoining air until the time it becomes fully charged. It discharges when the heat starts to flow out.In all instances of designing with thermal mass. In addition to the Arup report, many simulation-based studies have been undertaken to look at the relationship between insulation, ventilation, occupancy, as well as latitude.
Thermal mass and place of housing in the UK The properties of thermal lighting buildings and thermally heat buildingsThe fabric of the thermally light buildings is generally light in weight with little capacity to absorb and store heat. Thus these building display fast response to extral temperature changes. Thermal heavily buildings on contrast tend to be massive in their construction form insulates the interior form external changes as a result of slow reaction times.
The select construction form must be matched to climate, users’ needs and the building services that are present to activity modify the internal environmentThe thermal mass effectBuilding regulations in the UK focus on keeping buildings warm as efficiently as possible, but summer comfort is also important and as we experience periods of very hot weather, overheating is becoming an issue.One way to tackle this is to use materials with a high thermal mass. Materials that have a high thermal mass (such as masonry) will take a long time to heat up. On a hot summer’s day, a masonry wall will heat very slowly, allowing the temperature inside to stay comfortable. Heat absorbed by the masonry during the day will then be released slowly during the night ” keeping a relatively constant temperature inside the house throughout the 24 hour cycle.Lightweight building materials, on the other hand, will heat up and cool down very fast, contributing to significant temperature fluctuations inside the building. R unit mKW-1 The Conductance CWm-1K-1 the rate of heat flResistance Rm^2 The recipical of conductance and a measure of the resistance to heat flow for a given thicknessTransmittance U similar to conductance but also takes into account surface and air space resistance.(Wm^2K_1)2.2 the basic thermal dynamics backgroundAs the warm-blooded animals exposed to changing environment, human can control deep body temperature within narrow limits by adjusting the rate at which heat is produced by metabolism or dissipated by evaporation. They are therefore classes as homeotherms (thermal physics)Thermal comfort is the requirement of a balance of the heat we produce within our body (internal temperature) and the environment. (Nicol, Humphreys, and Roaf, 2012) There are three fundamental models to consider when defining thermal comfort criteria: the sociological approaches, physiological, and physical. (O’Callaghan, P.W., 1978) There are brief In the model of Psychophysics. The skin reacts like a sensation thermometer’ in human body to sense the external temperature and feeling varies from gender, age, culture, personality type, and the usual activities in the future. In the long term, people familiar with such environment they perform better in that climate. (Nicol, Humphreys, and Roaf, 2012) For example, changes in posture or activity can adjust the flow of metabolic heat, such as altering clothing insulation levels, or regulating the warm climate like opening a window. (O’Callaghan, 1978) There are bunch of other effects influence as the thermal comfort such as age, gender, health conditions, ethnic difference geographical location, Acclimatisation, expectations as well as the degree of occupant which we need to study and might need to consider when we simulate the group(note) The amount of the metabolic heat generated in the human body depend on the activities of humans and there are some studies related to the relationship and the amount I the thermal physics books. 1.1.6 Behavior Immediately, people will change clothes (like put on a coat). They can alter posture and metabolic rate and day by day they learn how to deal with weather conditions. Over a long period, they will able to change clothes for different seasons and know how to use the building and the activities to make them thermal comfort in a building. Ken Parson (2003)When room temperature future increase and reach around 25degrees, the human body starts to sweat, and water evaporated from the skin surface to absorb heat. (Nicol, Humphreys, and Roaf, 2012) The physiological model starts to be used as people are outside their comfort zone and they beaves as sweating, overregulation, and shivering. (O’Callaghan, 1978) The heat generated in the body by the metabolic process need to balance the heat lost in the environment and the core temperature in the human body must be controlled in closed limits to run the internal organs properly .(Nicol, Humphreys, and Roaf, 2012) In the physical model, the body is considered as a thermal system where heat is exchanged between the body tissues and the environment through the skin and clothing. (O’Callaghan, 1978) Equations are from Nicol, Humphreys, and Roaf (2012) and information are gathered from Parsons (2003) and the ASHRAE Handbook of Fundamentals (2009).Gains=losses(otherwise temp-infinite or zero) the Basic equation for thermal balance For the law of conservation of energy, the energy cannot be created or destroyed the total energy of an isolated system does not change. The energy can change forms all energy mechanical thermal or even light can be converted from one to another, so the energy in the house need to be in a balanceThe basic equation for thermal balance is: M-W=C+R+E+(C_res+E_res )+S (1.1)M is the metabolic rate (energy released in human body per unit time by the oxidation press)Metabolism(M)Standard measurements of the basal metabolic rate(BMR) are made when an animal has been deprived of food and is resting of food and is resting in an environment where metabolic rate is independent of external temperature. It has been widely accepted by animals physiologists that the basal metabolic rate of an animal Mb can be related to simply body mass W by the empirical allometric equationW is external mechanical work done C is the heat loss from the clothed body through convectionThe air movement around the human body without clothed can drive away the heat from the skin and rising over it forming a plume above the head and dispersing, and it is called natural convection.’ This kind of cooling or heating effect depends on the temperature difference between skin and air, and the air movement. (Nicol, Humphreys, and Roaf, 2012)R is the heat loss from the clothed body through radiation The radiation from heat surface is generally long-wave or infra-red radiation and is invisible, but it became visible when the surface is hot and contains heat. The mean radiational temperature is an artificial simplification which considers people as small spheres,’ and the value varies from place to place. (Nicol, Humphreys, and Roaf, 2012)E is the heat loss from the clothed body (sweat and insensible evaporation) through evaporationAn endothermic process happens when the water evaporates on the skin surface and extract a quantity of heat. Differences in water vapor pressure drive the evaporation and are defined as skin wittedness (W) (Nicol, Humphreys, and Roaf, 2012)The maximum rate of evaporation is given by E=h_c (P_ssk-Pa)W/m^2 (1.11)In the physical model, A human being is a heating body that lost their heat by convection, radiation, and evaporation. Overall, the heat lost in the human body will equal the heat gain from the environment. The three methods of heat transfer and other factors are discussed below. There are three main mechanism of the heat transfer Conduction Hotter particles are more energetic I Energy transferred through matter by direct contact I No change in basic positionConvection Hot air expands ’ less dense (lighter / m2) I Light air rises ’ buoyancy driven currents I Bulk motion of groups of molecules ’ Transport of heat and mixing of gassesRadiationEnergy transferred by electromagnetic radiation, I can pass through vacuum, air, transparent materials I transmission depends on wavelengthC_res is convective heat loss from respirationE_res is evaporative heat loss from respirationS is the rate at which heat is stored in the body tissuesThe equation for radiative heat transfers are R=µh_r f_cl f_eff (T_cl-T_r ) W/m^2 (1.2)R= rate of radiative heat flow per square metre of body surface›= the emissivity of the clothed /skin surface (generally close to 1)h_r= the linear radiation transfer coefficient (W/m^2K) (4.7 for typical clothing)f_(c_l )= the effective surface area of the clothed body (greater than one)f_eff= the effective radiation area factor (less than one, 0.7 when seated, 0.72 when standing (Fanger, 1970)T_cl= the clothing surface temperature (” )T_r= the mean radiant temperature (” )The equation for convective heat transfer is C=h_c (T_cl-T_a ) w€•m^2 (1.3)C is the rate of convective heat flow per square meter of body surface T_cl= the mean surface temperature of the clothed bodyT_a= the indoor air temperature h_c= the convective transfer coefficient in w€•m^2 K (3.1for V