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LECTURE 4: HEAT EXCHANGE PROCESS AND U-VALUE, download, images, images -…
LECTURE 4: HEAT EXCHANGE PROCESS AND U-VALUE
FACTORS AFFECT OF U-VALUE
U = 1/Rt
W/m2 K or W/m2 ̊C
THERMAL CONDUCTANCE(c)
THICKNESS OF A MATERIAL
W/m2 K or W/m2̊C
THERMAL CONDUCTIVITY
QUANTITY OF HEAT TRANSMITTED
THROUGH A UNIT AREA AND UNIT THICKNESS
IN UNIT TIME WHEN UNIT TEMPERATURE DIFFERENTIAL
EXPRESSED IN EQUATION AS:K=B/R
UNIT FOR THERMAL CONDUCTIVITY:W/mK OR W/m ̊C
DEFINITION OF THERMAL RESISTANCE
THERMAL RESISTANCE OF ANY SECTION OR ASSEMBLY OF BUILDING COMPONENTS
RECIPROCAL OF ITS THERMAL CONDUCTANCE
R=B/K
m2 K/W or m2̊C/W
HEAT TO AND FROM A SURFACE OF A BODY THOUGH AIR
INTRODUCTION
MAINTAIN A COMFORTABLE INTERNAL TEMPERATURE
WELL-DEFINED AMOUNT OF HEAT
BUILDING PURPOSE
SECURITY,PRIVACY
PROTECTION FROM WEATHER
PROVIDE SHELTER
HEAT EXCHANGE
HEAT TRANSFER FROM ONE PLACE TO ANOTHER UNTIL THE TEMPERATURE IS EQUAL
WARM TEMPERATURES
COLD TEMPERATURE
GAINING OR LOSING HEAT
CALCULATION
Qv = 1300 x V x ΔT
CONVECTION OF HEAT FLOW BETWEEN INTERIOR AND OPEN SPACE
Qc = A x U x ΔT
CONDUCTION THROUGH A WALL
Qs = A x I x θ
GLASSES SOLAR GAIN FACTOR AND ANGLE OF INCIDENCE
Qi = Activity x No.of occupants
INTERNAL HEAT GAIN
Qm
MECHANICAL CONTROL
PASSIVE DESIGN
ARCHITECTURAL DESIGN,BUILDING CONFIGURATION AND MATERIAL CHOICES
U-VALUE
LOW U-VALUE = GOOD INSULATOR
HEAT TRANSFER COEFFICIENTS
DEFINITION
HEAT FROM TRANSMITTING BETWEEN THE OUTSIDE AND INSIDE
LOW U-VALUE
GOOD INSULATOR
BETTER(LOWER) U-VALUE=MAINTAIN COMFORTABLE CONDITIONS
