Anna Majchrzycka THERMAL COMFORT

Transcription

1 WEST POMERANIAN UNIVERSITY OF TECHNOLOGY, SZCZECIN, POLAND THE FACULTY OF MECHANICAL ENGINEERING AND MECHATRONICS Anna Majchrzycka THERMAL COMFORT

2 ASHRAE STANDARD Thermal comfort is defined as that condition of mind that express satisfaction with the thermal environment.

3 FIRST LAW OF THERMODYNAMICS - ENERGY BALANCE E d = E w + E u Based on :

4 CONDUCTION Q λ ( t t )A δ Q= w1 w2 t w1 t w2 CONVECTION t f1 Q 2 α 1 ( t t )A Q= f1 w1 α Q = α 2 ( t t )A Q w2 f2 Q t w1 α 1 t w2 t f2 HEAT TRANSMISSION k( t t )A Q= f1 f2 t f1 =t

5 E d =? E u =? E w =? t f1 = t=?

6 Passive house Standard house YEARLY HEAT LOSSES IN PASSIVE AND STANDARD HOUSE SOURCE: M.B.NANTKA:WENTYLACJA I ENERGIA W BUDOWNICT WIE TRADYCYJNYM I PASYWNYM, CZ.2 ENERGIA I BUDYNEK, 02 (12),2008

7 Standard house Passive house HEATING REQUIREMENT FOR STANDARD AND PASSIVE HOUSE SOURCE: M.B.NANTKA:WENTYLACJA I ENERGIA W BUDOWNICT WIE TRADYCYJNYM I PASYWNYM, CZ.2 ENERGIA I BUDYNEK, 02 (12),2008

8 OIL CONSUMPTION FOR HOUSE HEATING IN EUROPE CURRENT - 18 l / m 2 year NEAREST FUTURE - 5 l / m 2 year

9 HOLISTIC CONCEPT OF HOMESPACE EQUILIBRIUM BETWEEN QUALITY OF HOUSE, ESTHETICS AND ENERGY THAT COMES FROM LIGHT AND HEATING

10 HEATING COOLING BUILDING DESIGN & LAYOUT AIR MOVEMENT AIR CONDITIONING

11 ULTRA-LOW LOW ENERGY BUILDINGS Space heating requirement Construction costs Design and construction

12 Design and construction Passive solar design Energy storage, Superinsulation, Advanced window technology, Airtightness, Ventilation, Space heating, Lighting and electrical appliances.

13 THE MOST IMPORTANT FACTORS INFLUENCING THERMAL COMFORT ACTIVITY LEVEL THERMAL RESISTANCE OF CLOTHING AIR VELOCITY AIR RELATIVE HUMIDITY MEAN RADIANT TEMPERATURE AIR TEMPERATURE

14 THE OTHER FACTORS THAT CAN INFLUENCE THERMAL COMFORT VERTICAL TEMPERATURE DIFFERENCE, ASYMETRIC FIELD OF TEMPERATURE, DRAFT, HEAT OR COLD FLOOR, COLOURS, AGE, SEX, ETHNIC DIFFERENCES,ETC.

15 SYSTEMS OF AIR DISTRIBUTION IN BUILDINGS UPWARD FLOW SYSTEM DOWNWARD FLOW SYSTEM SOURCE: F.PORGES-HVAC ENGINEERS HANDBOOK, IX ED,1991

16 SYSTEMS OF AIR DISTRIBUTION IN BUILDINGS HIGH LEVEL SUPPLY AND RETURN SYSTEM SOURCE: F.PORGES-HVAC ENGINEERS HANDBOOK, IX ED,1991

17 SYSTEMS OF AIR DISTRIBUTION IN BUILDINGS LOW LEVEL SUPPLY AND RETURN SYSTEM EJECTOR SYSTEM SOURCE: F.PORGES-HVAC ENGINEERS HANDBOOK, IX ED,1991

18 Vertical temperature distribution for the different types of heating Floor electric heating Ideal profil Convective heaters placed on the internal walls Air heating

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20 Floor covering properties The contact coefficient ient b= λ ρ c

21 COLOUR,,WARM COLOURS,,COOL COLOURS As colour has no thermal INFLUENCE ON MAN, any influence on thermal sensation must therefore be of a psychological nature.

22 CROWDING the convective heat transfer will be impaired, mean radiant temperature will increase, added heat sources of the occupants.

23 AGE People over 40 years of agree prefere comfort temperature t=1k effective higher than that desired for persons below that age.

24 NOISE

25 E d = E w + E u RESPIRATION EVAPORATION METABOLIC HEAT CONDUCTION CONVECTION RADIATION Du Bois area A = m h where: m- body mass, kg h-height, height, m MECHANICAL WORK

26 Relationship between skin temperature and ambient temperature

27 SET POINT = t core t = t e - t core EFFECTOR PROPORTIONAL - PLUS DERIVATIVE CONTROLLER INPUT SIGNAL = t e COMPARATOR Y e - Y set point GOOSE SKIN dt =α dτ Output SHIVERING BLOOD FLOW SWEATING Heat gain or loss THERMORGULATORY SYSTEM OF HUMAN BODY

28 SKIN HEAT AND COLD THERMORECEPTORS INTERNAL ORGANS MUSCLES CENTRAL NERVOUS SYSTEM BREATHING SYSTEM SKIN BLOOD VESSELS SWEAT GLANDS

29 t o Set point TERMPERATURE DEVIATION Y t TIME THERMOREGULATORY SYSTEM WITH PROPORTIONAL TEMPERATURE REGULATION

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31 THERMAL BALANCE OF THE HUMAN BODY Q& m - W& - (Q& d + Q& Q m METABOLIC HEAT - HEAT LOSS BY SKIN DIFFUSION - HEAT LOSS BY EVAPORATION OF SWEAT- LATENT RESPIRATORY HEAT LOSS- DRY RESPIRATORY HEAT LOSS - Q & HEAT CONDUCTION THROUGH CLOTHING- + Q& u Source :Thermal Comfort, P. O. Fanger, McGraw-Hill, New York, & e + Q& j + Q& m HEAT LOSS BY RADIATION - HEAT LOSS BY CONVECTION - MECHANICAL POWER - k W & = Q & + W& (2) + Q& r Q & Q & k Q & j d Q & u ) = ±S& Q & Q p Q & e (1)

32 THERMAL HOMEOSTASIS, t core = 37 o C S & = 0 (3) core CONDITIONS FOR THERMAL COMFORT Q & - (Q & d + Q & e + Q & u + Q & j ) = Q & P = Q & k + Q & r (4) A < t s < B (5) C < Q & e < D (6)

33 THE COMFORT TEMPERATURE t = f(v,qm, & ϕ,tr,icl ) [ 7 ]

34 INTERNAL HEAT PRODUCTION INTERNAL BODY HEAT Q= & Q& m - W & (8) EXTERNAL MECHANICAL EFFICIENCY η= W& & Qm (9)

35 METABOLIC HEAT Q& m = CV& = q& O2 m A Du (10) O 2 C= J/cm 3 Q& = (1- C (1- η) V& O 2 = (1- η) Q& m = η) q& m A Du (11)

36 Table 1. Metabolic Heat Generation Rates Activity q& m [W/m 2 ] 1 Lying down 47 2 Quietly seated 58 3 Sedentary activity (office, home, school) 58 4 Standing, relaxed 70 5 Light activity (shopping, laboratory, light work) 93 6 Medium activity (shop work, domestic work, 117 machine work) 7 Heavy activity (heavy machine work, garage work Heavy exercise (running) 525 Thermal Comfort, P. O. Fanger, McGraw-Hill, New York, 1970.

37 HEAT LOSS BY PERSPIRATION (BY SKIN DIFFUSION) Q& d =β r ADu (ps - ϕ psw ) (12) β ps = 256 t s 3360,(13) - evaporation coefficient, [kg/m 2 spa] A du - Du Bois area,[ m 2 ] p s, p sw pressure of saturated vapor, pressure of vapour at ambient temperature, [Pa] r - ϕ heat of vaporization of water, [J/kg] - the relative humidity of the gas

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40 Relative Humidity ϕ, [%] MILEDEW Optimum Relative Humidity ϕ= 45% - 55%

41 LEARNING ABOUT HUMIDITY IN THERMAL COMFORT ROSET, J.,MARINCIC, I.; OCHOA, J.M.; SERRA, R.

42 Evap poration coefficient, [kg/m 2 spa] 5,90E-08 5,70E-08 5,50E-08 5,30E-08 5,10E-08 4,90E-08 4,70E-08 4,50E-08 β = (4,58 + 3,46 v) 10 8, [kg/m 2 spa] 0 0,1 0,2 0,3 0,4 Air velocity v, [m/s] Source : Andjulovici A., Georgescu S.- Confortul termic in cladiri,ed.tehnica, Bucuresti 1966, Arkady, Warsaw 1971.

43 HEAT LOSS BY EVAPORATION OF SWEAT Q& e = w β r A Du (p s - ϕ p sw ) (14) Skin wetness is defined as: w = & Qe & Qemax = 0,02+ 0,4 qm & 58 { 1 - exp [- 0,6 ( -1)} (15) Azer N.Z, Hsu S. The use of modeling human response in the analysis of thermal comfort of indoor environmens. Proceedings of a Symposium held at the National Bureau of Standards, February, 1977.

44 0,30 0,25 WETNESS SKIN 0,20 0,15 0,10 0,05 0,00 Q& e q& w = = 0,02 + 0,4 1 exp 0,6 m 1 Q& emax Metabolic activity, q m, [W/m 2 ]

45 RESPIRATORY HEAT LOSS LATENT RESPIRATON HEAT LOSS DRY RESPIRATION HEAT LOSS

46 DRY RESPIRATORY HEAT LOSS Dry respiratory heat loss results from the difference between the expired and inspired gas temperatures: Q& j = m& cp ADu (tex - ti) (16) cp - specific heat at the constant pressure, J/kgK m& - mas rate of gas, kg/s t, - the temperature of the expired, inspired gas, o C ex t i

47 LATENT RESPIRATORY HEAT LOSS & Qu = m& r (Xex - Xin) = = 1, q& m A Du (X ex - X in )(17) m& - mas rate of gas, kg/s r - heat of water evaporation, kj/kg, X ex,x in - humidity ratio of the expired, inspired gas

48 HEAT CONDUCTED THROUGH THE CLOTHING Q & p = (t s - t cl )A Du R cl (18) I cl = R cl 0,155 m 2 K 1clo= 0,155 (19) W (20) A Du - Du Bois area,m 2 I cl - thermal resistance from skin to the surface of the clothing, clo, t cl, t s - the temperature of the outer surface of the clothing, skin o C, R cl - thermal resistance from skin to the surface of the clothing,m 2 K/W

49 Thermal Insulation of Clothing The addition of thermal resistance due to clothing affects heat transfer mechanisms between the human body and the environment. Clo- value is a numerical representation of a clothing ensemble's thermal resistance, 1 clo = m 2 K / W.

50 Thermal resistance of different clothyhing ensembles Clothing Combination I cl, [clo] R cl [m2-k/w] Naked 0 0 Shorts Tropical ensemble (briefs, shorts, open- necked shirt, light socks and sandals) Light summer ensemble (briefs, long lightweight trousers, short-sleeved shirt, light socks and shoes) Working attire (briefs, longsleeved shirt, trousers, woolen socks and shoes) Typical indoor winter attire (briefs, long-sleeved shirt, trousers, long-sleeveds weater, heavy socks and shoes) Heavy indoor winter attire (long underwear, long-sleeved shirt, suit with vest, heavy socks and shoes) Source:Thermal Comfort, P. O. Fanger, McGraw-Hill, New York, 1970.

51 HEAT LOSS BY RADIATION HEAT LOSS BY RADIATION Q & ,15) 4 R = 4 10 fcl ADu [(tcl + - (tr ,15) ] (21) f cl - the ratio of the surface area of the clothed body to the surface of the nude body, t, t r - the comfort, mean radiant temperature, o C, A Du - Du Bois area, m 2

52 HEAT LOSS BY CONVECTION Q& k = αfcladu(tcl - t) (22) C p - specific heat at the constant pressure, J/kgK f cl - clothing factor, p - total pressure of the breathing mixture, Pa, v - relative velocity of gas, m/s t, t r - the comfort, mean radiant temperature, o C, λ - thermal conductivity of the breathing gas, W/mK, x i - molar fraction of the inert gas

53 Convective heat transfer coefficient: α= f(c p, λ, η, ρ,t,v) (23) FREE CONVECTION, MIXED CONVECTION, FORCED CONVECTION C p - specific heat at the constant pressure, J/kgK v - relative velocity of gas, m/s t - the comfort, mean temperature, o C λ - thermal conductivity of the breathing gas, W/mK, v - air velocity, m/s, η - dynamic viscosity coefficient, kg/ms

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55 THE COMFORT EQUATION (1 η) qm & - β r (ps - ϕ psw ) + - w β r (ps - ϕ psw ) - + 1, q& m r (X ex - X in ) - m& c p (t ex t) = t = s t cl =α f cl A Du (t cl - t) 0,155 I cl f A [(t 273,15) 4 cl Du cl + - (t r ,15) ] (23)

56 THE COMFORT TEMPERATURE t = f(v,q&, ϕ,t m m r,i cl )

57 ENVIRONMENTAL VARIABLES -AIR TEMPERATURE: -MEAN RADIANT TEMPERATURE: t tr -AIR RELATIVE VELOCITY: v -HUMIDITY OF AIR: ϕ HUMAN VARIABLES - ACTIVITY OF MAN: V & o2, q & - PARAMETERS OF THE BODY (MASS, HEIGHT): m m,h, A Du CLOTHING VARIABLES - THERMAL RESISTANCE OF THE CLOTHING: - MOISTURE PERMEATION FACTOR : Fpcl I cl

58 W q& m m Source:Thermal Comfort, P. O. Fanger, McGraw-Hill, New York, 1970.

59 q& m W 58 m 2 Source:Thermal Comfort, P. O. Fanger, McGraw-Hill, New York, 1970.

60 W q& m m Source:Thermal Comfort, P. O. Fanger, McGraw-Hill, New York, 1970.

61 Source:Thermal Comfort, P. O. Fanger, McGraw-Hill, New York, 1970.

62 Source:Thermal Comfort, P. O. Fanger, McGraw-Hill, New York, 1970.

63 COMFORT ZONE

64 ENVIRONMENTAL INDICES MEAN RADIANT TEMPERATURE PREDICTED MEAN VOTE (PMV) INDEX PREDICTED PERCENTAGE DISSATISFIED (PPD) INDEX LOWEST POSSIBLE PERCENTAGE DISSATISFIED (LPPD) INDEX THE OPERATIVE TEMPERATURE

65 MEAN RADIANT TEMPERATURE the uniform surface temperature of a black enclosure with which an individual exchanges the same heat by radiation as the actual environment considered.

66 PREDICTED MEAN VOTE (PMV) INDEX The PMV index predicts the mean response of a large group of people according to the ASHRAE thermal sensation scale:

67 where M( q m ) - metabolic rate L - thermal load defined as the difference between the internal heat production and the heat loss to the actual environment for a person hypothetically kept at comfort values of skin temperature and evaporative heat loss by sweating at the actual activity level.

68 PMV method can be described as a simple energy balance, in which a human comfort index is estimated from a difference in heat generated by the human body with the heat lost from the body to the surroundings.

69 PREDICTED PERCENTAGE DISSATISFIED (PPD) INDEX PPD is a quantitative measure of the thermal comfort of a group of people at a particular thermal environment. Fanger related the PPD to the PMV as follows:

70 Source:Thermal Comfort, P. O. Fanger, McGraw-Hill, New York, 1970.

71 LOWEST POSSIBLE PERCENTAGE DISSATISFIED (LPPD) INDEX The LPPD is a quantitative measure of the thermal comfort of a room as a whole for a group of people in a thermally nonuniform environment. It is more useful for large rooms than for small one. As a recommended design target, LPPD is not to exceed 6%.

72 THE OPERATIVE TEMPERATURE Is one of several parameters devised to measure the air's cooling effect upon a human body It is equal to the dry-bulb temperature at which a specified hypothetical environment would support the same heat loss from an unclothed, reclining human body as the actual environment. In the hypothetical environment, the wall and air temperatures are equal and the air movement is 7.6 cm/s.

73 From experiment it has been found that the operative temperature where: t r is the mean radiant temperature; ( o C), t a is the mean air temperature; ( o C), t s is the mean skin temperature; ( o C), and v is the airspeed, cm/s.

74 Effective Temperature Effective temperature is the uniform temperature of a radiantly black enclosure at 50% relative humidity, in which an occupant would experience the same comfort, physiological strain and heat exchange as in the actual environment with the same air motion.

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