Heat Transfer SmartBook 3
A cylindrical pipe is to establish a heat conduction at a rate of 270 W. If the sides of the pipe are maintained at a temperature difference is 25 K, calculate its conduction resistance.
(0.093) K/W
Calculate heat conduction rate through a pipe if temperatures on the two sides of the wall, T1T1 and T2T2. are maintained at 323.15 K and 291.15 K, respectively, and the conduction resistance of the material is (2.06 x 10−310-3) K/W.
(15.53 x 103103) W
If the driving potential (∆T∆T) and the rate of heat conduction (Q˙condQ˙cond) are 13 K and 750 W. respectively, calculate the conduction resistance (RcylRcyl) of the system.
(17.33 x 10−3) KW
If the fin tip is assumed to be adiabatic, the temperature distribution can be expressed by the equation _____.
(T(x)-T∞)/(Tb-T∞) = coshm(L-x)/coshmL
The rate of heat transfer (Q˙)Q˙ through a medium can be calculated using the formula _____, where U is the overall heat transfer coefficient, A is the heat transfer area, and ∆T∆T is the temperature difference across the boundaries of the medium.
(U)(A)(deltaT)
If the length of the fin (L) is 0.19 m, the corrected fin length (Lc) is 0.23 m, and the perimeter (p) of the fin is 0.04 m, calculate the cross-sectional area (Ac) of the fin.
0.0016 m2
The total thermal resistance of a system is 36.7 K/W and the area of heat transfer is 1.02 m2. Calculate the overall heat transfer coefficient for the system.
0.027
The total thermal resistance of a system is 36.7 K/W and the area of heat transfer is 1.02 m2. Calculate the overall heat transfer coefficient for the system.
0.027 Wm2⋅K
For a plane wall system, if the convection heat transfer coefficient (h)h is 14 Wm2⋅KWm2⋅K and the convection resistance (Rconv)Rconv is 2.1 KWKW, calculate the area of solid (As)As.
0.034 m2
For a system, if the rate of heat transfer through the interface (Q˙interface)Q˙interface is 14 W and the temperature difference across the interface (∆Tinterface)∆Tinterface is 6 K, calculate the area of the interface (A). Assume the thermal contact conductance (hchc) to be 45 Wm2·KWm2·K.
0.052 m2
A plane wall has thickness 0.1 m, cross-sectional area 1.2 m2, and thermal conductivity 0.8 W/(m⋅K). Calculate the conduction resistance of the material.
0.104 KW
Calculate the radiation resistance for a piece of coal with radiation heat transfer coefficient 7.33 W/(m2⋅K) and the surface area 1.2 m2.
0.11 KW
The corrected length of a fin is 0.18 m. The cross-sectional area and perimeter are 0.0016 m2 and 0.06 m, respectively. Calculate the length of the fin.
0.153
A fin with an insulated tip has an area of cross-section 0.0009 m2 and perimeter 0.03 m. The length of the fin is 0.14 m. Calculate the corrected length of the fin.
0.17 m Lc = L + Ac/p.
Calculate the radiation heat transfer coefficient for a body at 330 K with surface area 1.2 m2m2. The air around the body is at 298 K and the rate of radiation heat transfer is 7.4 W. Assume heat transfer occurs by radiation only.
0.19 Wm2·K
The convection heat transfer coefficient (h) for a body is 221 W/m2⋅K and the thermal conductivity (k) is 42 W/m⋅K for a cylindrical body. Calculate the critical radius (rcr, cylinder) of the body shown in the figure.
0.19 m
A copper plate with surface area 0.1 m2 is placed in oil. Calculate the convection resistance for oil if the convection heat transfer coefficient for oil is 50 W/(m2⋅K).
0.20 KW
Calculate the corrected fin length for a cylindrical fin with diameter 0.02 m and length 0.20 m.
0.205 m Lc,cylinder = L + D/4
Calculate the corrected fin length for a rectangular fin with thickness 0.02 m and length 0.20 m
0.21
A long fin has efficiency (ηfin)ηfin 0.87, perimeter (p) of the fin tip 0.12 m, area of cross-section (Ac) 0.0016 m2, convection heat transfer coefficient (h) 35 W/m2⋅K, and thermal conductivity (k) 96 W/m⋅K. Calculate the length (L) of the fin.
0.22 m
The interface temperature difference is 6 K for the interface between two metal bodies in contact. The rate of heat transfer is 16.3 W and the area is 1 m2m2. Calculate the thermal contact resistance for the entire interface.
0.37 KW
The convection heat transfer coefficient (h) is 221 W/m2⋅K and the thermal conductivity (k) is 42 W/m⋅K for a spherical shell. Calculate the critical radius (rcr, sphere) of the body, shown in the figure.
0.38 m
For a long fin of length (L) 0.28 m, calculate the fin efficiency (ηfin). Consider the fin to be a long fin and m = 6 m-1.
0.59 ηfin = 1/(m×L)
For a system, if the overall heat transfer coefficient (U)U is 0.94 Wm2⋅KWm2⋅K and the area of heat transfer (A)A is 1.07 m2, calculate the total resistance (Rtotal)Rtotal.
0.99 KW
Rank the following values of the rate of heat transfer (Q˙in)Q˙in into a wall and the rate of change of the energy (dEwalldt)dEwalldt of the plane wall from the smallest to largest order of rate of heat transfer (Q˙out)Q˙out out of the wall. Place the smallest value on top.
1) 17 2) 15 3)9
The outer and inner radii of a cylinder are 0.5 m and 0.3 m, respectively. The length of the cylinder is 1.2 m and the thermal conductivity of the material is 42 W/m⋅K. Calculate the conductive thermal resistance of the cylinder.
1.61 × 10-3 KW
The thermal network shown in the figure has R1 = 6 KWKW, R2 = 1.8 KWKW, and R3 = 9 KWKW. Calculate the total resistance of the network. Assume heat transfer takes place by conduction only.
10.38 KW
Calculate the rate of heat transfer through an interface (Q˙interface)Q˙interface if the rate of heat transfer through contact patches (Q˙contact)Q˙contact is 6 W and the rate of heat transfer through the gaps (Q˙gap)Q˙gap in the contact is 4.5 W.
10.5 W
For the multi-layered wall shown in the figure, if the coefficient of convection heat transfer for the two fluids (h1 and h2)h1 and h2 are 13 Wm2·KWm2·K and 15 Wm2·KWm2·K, respectively, the thermal conductivities (k1 and k2)k1 and k2 of the two plane wall are 1.24 Wm2·KWm2·K and 0.57 Wm2·KWm2·K, respectively, the area (A) of the plan wall is 2 m2m2, the thickness of the walls are (L1 and L2)L1 and L2 0.13 m and 0.17 m, respectively, and the temperatures (T∞1T∞1 and T∞2T∞2) are 330 K and 295 K, respectively, calculate the rate of heat transfer (Q˙)Q˙.
128.047
For a plane wall system, the convection heat transfer rate (Qconv)Qconv is 20 W and the convection resistance (Rconv)Rconv is 0.77 K/W, calculate the temperature difference (Ts − T∞)Ts - T∞ between the plane wall and the surrounding fluid.
15.4 K
Calculate the rate of change of the energy of the wall (dEwalldt) if the rate of heat transfer into the wall (Q˙in)is 60 W and the rate of heat transfer out of the wall (Q˙out) is 43 W.
17 W
For a system, if the overall heat transfer coefficient (U)U is 3.37Wm2·KWm2·K, the value of heat transfer (Q˙Q˙) is 101 W, and the surface area is 1.6 m2m2, calculate the temperature gradient (∆T∆T).
18.73 K
For a plane wall, the conduction resistance (Rwall)Rwall is 11.90 × 10-310-3 K/W, the thermal conductivity (k)k is 2.10 W/(m⋅K), and the thickness (L)L is 0.05 m. Calculate the cross-sectional area of the wall.
2 m2
The outer and inner radii of a sphere are 0.5 m and 0.3 m, respectively. The thermal conductivity of the material is 42 W/m⋅K. Calculate the conductive thermal resistance of the sphere.
2.53 × 10-3 KW Rsph = r2-r14×π×r2×r1×kr2-r14×π×r2×r1×k.
The given figure shows a thermal network with T∞1T∞1 = 325.15 K, T1T1 = 310.15 K, RwallRwall = 0.08 KWKW, and Rconv,1Rconv,1 = 0.036 KWKW. Calculate the value of temperature T2T2 if the thermal network is under steady state conditions.
276.82 K
The given figure shows a thermal network with T1T1 = 290.15 K, T2T2 = 282.15 K, RwallRwall = 0.07 KWKW, and Rconv,2Rconv,2 = 0.02 KWKW. Calculate the value of temperature T∞2T∞2 if the thermal network is under steady state conditions.
279.86 K
For a system, if the heat transfer through the interface (Q˙interface)Q˙interface is 0.75 W, thermal contact resistance per unit area (RcRc) is 58 m2·KWm2·KW, and the temperature difference across the interface (∆T˙interface)∆T˙interface is 14 K, calculate the area of the interface (A).
3.11 m2
The given figure shows a thermal network with T2T2 = 295.15 K, T∞2T∞2 = 287.15 K, RwallRwall = 0.037 KWKW, and Rconv,2Rconv,2 = 0.017 KWKW. Calculate the value of temperature T1T1 if the thermal network is under steady state conditions.
312.56 K
The given figure shows a thermal network with T2T2 = 295.15 K, T∞2T∞2 = 287.15 K, RwallRwall = 0.037 KWKW, and Rconv,2Rconv,2 = 0.017 KWKW. Calculate the value of temperature T1T1 if the thermal network is under steady state conditions.
312.56 K Reason: Here the conductive resistance (RwallRwall) is calculated by the expression T∞2-T1RwallT∞2-T1Rwall = T1-T2Rconv,2T1-T2Rconv,2, and hence this option is wrong. The answer is obtained using the law of conservation of energy that states T2-T∞2Rconv,2T2-T∞2Rconv,2 = T1-T2RwallT1-T2Rwall for the given situation.
A square-steel section of cross-sectional area 0.24 m2m2, thickness 0.075 m, and the thermal conductivity 50.2 W/(m·K)W/(m·K) is subjected to a temperature difference of 20 K between its two faces. Calculate the heat transfer rate through the section if it acts like a plane wall.
3212.8 W
The convection heat transfer coefficient is 32 Wm2·KWm2·K and the radiation heat transfer coefficient is 2.6 Wm2·KWm2·K. Calculate the combined heat transfer coefficient.
34.6 Wm2·K
For the thermal network shown in the figure, rate of heat transfer (Q˙)Q˙ through the system is 0.67 W, total thermal resistance (Rtotal)Rtotal for the network is 44.78 KWKW, and T∞2T∞2 is 350 K. Calculate the value of T∞1T∞1.
380 K
The interface temperature difference is 23 K for the interface between two metal bodies in contact. The area of the interface is 0.5 m2m2 and thermal contact resistance per unit area for the interface is 2.7 m2·KWm2·KW. Calculate rate of heat transfer through the entire interface.
4.26 W
The thermal contact conductance of an interface between two metal plates in contact is 200 W/m2·KW/m2·K. The area of the interface is 0.08 m2m2 and the temperature difference at the interface is 3 K. Calculate the rate of heat transfer for the interface.
48 W
For the network, shown in the figure, if the rate of heat transfer (Q˙)Q˙ through the network is 2 W and the temperatures T∞1T∞1 and T∞2T∞2 are 307 K and 295 K, respectively, calculate the value of total resistance (Rtotal)Rtotal of the network.
6 KW
Identify the true statements about heat conduction in a wall if the air temperatures inside and outside the house remain constant.
A small thickness of the wall causes the temperature gradient in that direction to be large. Heat transfer through the wall of a house can be modeled as steady and one-dimensional.
The desired temperature distribution when the temperature at the end of the fin is fixed at a specified temperature is given by the equation T(x)-T∞Tb-T∞T(x)-T∞Tb-T∞ = a+bca+bc. Match a, b, and c (in the left column) with the corresponding terms (in the right column).
A) Long one B) sinh m(L-x) C) sinh mL
Identify the assumptions used to solve multidimensional heat transfer problems by treating them as one-dimensional in the x-axis.
Any plane wall normal to the x-axis is isothermal. Any plane parallel to the x-axis is adiabatic.
True or false: The equation for convection resistance RconvRconv = 1h×As1h×As is valid only when the surfaces are plane. h is the convection heat transfer coefficient and As is the cross-sectional area of the solid.
False
For a thermal system, identify the correct statement about fins.
Fins enhance heat transfer from a surface by exposing a larger surface area to convection and radiation.
Two brass plates are held together using rivets. Which of the following are true of the thermal contact resistance between these two plates.
It depends on the size of the contact zone. It depends on the type of fluid trapped in the interface.
The corrected length (Lc,cylindrical)Lc,cylindrical for a cylindrical fin can be calculated using the formula _____. "D" is the diameter of the fin, and "L" is the length of the fin.
L + (D/4)
The corrected length (Lc) for a fin with an insulated tip can be calculated using the formula _____. Here Ac is the cross-sectional area of the fin, p is the perimeter of the fin, and L is the length of the fin.
Lc = L + Ac/p
The corrected length (Lc,cylindrical) for a cylindrical fin can be calculated using the formula _____. "D" is the diameter of the fin, and "L" is the length of the fin.
Lc,cylindricalLc,cylindrical = L + D/4
The corrected length (Lc,rectangular)Lc,rectangular for a rectangular fin can be calculated using the formula _____. "t" is the thickness area of the fin, and "L" is the length of the fin.
Lc,rectangular= L + t/2
If "R" is used to represent the thermal resistances for the thermal network shown in the figure, under steady state conditions, the rate of heat transfer (Q˙)Q˙ can be calculated using the formula _____.
Q˙ = (T1 − T2)/Rwall Q˙ =( T∞ 1 − T1)/Rconv 1 Q˙ = (T2 − T∞2)/Rconv 2
For the cylindrical pipe shown in the figure, the rate of heat transfer (Q˙Q˙) can be calculated using the formula ____, where L is the length of the pipe.
Q˙ = (T1 − T∞)/[ln (r2/r1)2πLK + 1h(2πr2L)]
For the thermal network given in the figure, the relationship between the rate of heat transfer (Q˙)Q˙ through the system and the total thermal resistance (Rtotal)Rtotal can be represented using the formula ____.
Q˙ = T∞1 − T∞2Rtotal
The rate of heat transfer (Q˙)Q˙ through a medium can be calculated using the formula _____, where U is the overall heat transfer coefficient, A is the heat transfer area, and ∆T∆T is the temperature difference across the boundaries of the medium.
Q˙ = U x A x ∆T
The Fourier's law for heat conduction for the plane wall shown in the figure is given by _____. Q˙cond is the rate of conduction heat transfer, k is the average thermal conductivity, A is the cross-sectional area of the material, T1 − T2 is the temperature difference, and L is the wall thickness.
Q˙cond = kA x (T1 − T2)L
The rate of convective heat transfer between a solid and a fluid can be calculated using the formula ______, where Q˙convQ˙conv is the rate of convection heat transfer, T∞T∞ is the temperature of the solid, TsTs is the temperature of the liquid, and RconvRconv is the convection resistance.
Q˙conv = Ts − T∞Rconv
The energy balance equation for a plane wall section is given by _____. Q˙inQ˙in is the rate of heat transfer into the wall, Q˙outQ˙out is the rate of heat transfer out of the wall, dEwalldtdEwalldt is the rate of change of the energy of the wall.
Q˙inQ˙in - Q˙outQ˙out = dEwalldt
The steady rate of heat transfer from the entire fin, determined from Fourier's law of heat conduction is _____ , where Q˙long finQ˙long fin is the rate of conduction heat transfer through the long fin, h is the heat transfer coefficient, k is the constant thermal conductivity, AcAc is the constant cross-sectional area of the fin, p is the perimeter of the fin, TbTb is the temperature at the base of the fin, and T∞T∞ is the temperature of the surrounding fluid (Tb >T∞)Tb >T∞.
Q˙long fin = (Tb − T∞) √(hpkAc)
Identify the correct statement about the thermal network shown in the figure under steady-state conditions.
Rate of heat convection into the wall (Q˙1)Q˙1 = Rate of heat convection from the wall (Q˙2)Q˙2.
With reference to the plane wall shown in the figure, which of the following are true of the rate of heat transfer between the plane wall and its surfaces under steady-state conditions?
Rate of heat convection through the wall (Q˙wall)Q˙wall = Rate of heat convection from the wall (Q˙2) Rate of heat convection into the wall (Q˙1)Q˙1 = Rate of heat conduction through the wall (Q˙wall)
The thermal contact resistance (RcRc) for an interface between two metals in contact can be calculated using the formula _____, where A is the area of interface, Q˙interfaceQ˙interface is the rate of heat transfer through the interface, and ∆Tinerface∆Tinerface is the temperature difference across the interface.
Rc = ∆Tinterface x AQ˙interface
The equation used to determine the conduction thermal resistance (Rcyl) for a cylinder is _____. Here r1 is the inner radius, r2 is the outer radius, L is the length, and k is the thermal conductivity.
Rcyl = (ln(r2/r1))/(2×π×L×k)
The equation used to determine the conduction thermal resistance (Rcyl) for a cylinder is _____. Here r1 is the inner radius, r2 is the outer radius, L is the length, and k is the thermal conductivity.
Rcyl = lnr2r12×π×L×k
If the driving potential (∆T) and the rate of heat conduction (Q˙cond) are 13 K and 750 W. respectively, calculate the conduction resistance (Rcyl) of the system.
Rcyl = ∆TQ˙condRcyl = ∆TQ˙cond Rcyl = 13 K750 WRcyl = 13 K750 W RcylRcyl = (17.33 x 10−3) KW
A plane concrete wall has a thickness of 0.3 m and area of cross-section 25 m2. The thermal conductivity of concrete is 1.09 W/(m·K). The temperature on one side of the wall (T1) is 32°C and the other side (T2) is 17°C. Calculate the rate of heat conduction through the plane wall.
Reason: (Q˙cond) = ((A) x Thermal conductivity (k) xTemperature difference (T1 − T2)/Thickness (L)) that yields (Q˙cond)=1362.5 W
The given figure shows a thermal network with T∞2T∞2 = 276.15 K, T1T1 = 285.15 K, T2T2 = 278.15 K, and Rconv,2Rconv,2 = 0.012 KWKW. Calculate the thermal resistance of the wall (Rwall)Rwall if the thermal network is under steady-state conditions.
Reason: Here the conductive resistance (RwallRwall) is calculated by the expression T∞2-T1RwallT∞2-T1Rwall = T1-T2Rconv,2T1-T2Rconv,2, and hence, this option is wrong. The answer is obtained using the law of conservation of energy that states T2-T∞2Rconv,2T2-T∞2Rconv,2 = T1-T2RwallT1-T2Rwall for the given situation. 0.042 KW
The heat transfer coefficient (h) of a very long fin is 25 W/(m2·K)m2·K, the constant thermal conductivity (k) is 205 W/(m·K)m·K, the constant cross-sectional area of the fin (Ac)Ac is 0.01 m2m2, the perimeter of the fin (p) is 0.2 m, the temperature at the base of the fin (TbTb) is 325 K, and the temperature of the surrounding fluid (T∞T∞) is 300 K. The steady rate of heat transfer from the entire fin, determined from Fourier's law of heat conduction, is _____, where Q˙long finQ˙long fin is the rate of heat transfer from a long fin.
Reason: Here the root of hp/kAc 80 Q
The given figure shows a thermal network with T1T1 = 290.15 K, T2T2 = 282.15 K, RwallRwall = 0.07 KWKW, and Rconv,1Rconv,1 = 0.03 KWKW. Calculate the value of temperature T∞1T∞1 if the thermal network is under steady-state conditions.
Reason: Here the temperature is calculated by the expression T∞1-T2Rconv,1T∞1-T2Rconv,1 = T1-T2RwallT1-T2Rwall, and hence, this option is wrong. The answer is obtained using the law of conservation of energy that states T∞1-T1Rconv,1T∞1-T1Rconv,1 = T1-T2RwallT1-T2Rwall for the given situation. 293.58 K
The equation used to determine the conduction thermal resistance (Rsph) for a sphere is _____. Here r1 is the inner radius, r2 is the outer radius, and k is the thermal conductivity.
Rsph = (r2-r1)/(4×π×r2×r1×k)
For the thermal network shown in the figure, the total resistance (Rtotal) can be calculated using the formula _____. R1, R2, R3 are the thermal resistance for the material 1, 2, and 3, respectively. Assume heat transfer takes place by conduction only.
Rtotal = (R1×R2)/(R1+R2) + R3
For the thermal network given in the figure, the total thermal resistance (Rtotal)Rtotal system can be calculated using the formula _____, where A is the heat transfer area, k is the thermal conductivity and h is the heat transfer coefficient.
Rtotal = 1/h1×A1h1×A + L1/k1×AL1k1×A + L2/k2×AL2k2×A + 1/h2×A
For the thermal network given in the figure, the total thermal resistance (Rtotal)Rtotal can be calculated using the formula _____, where A is the heat transfer area, k is the thermal conductivity, and h is the heat transfer coefficient.
RtotalRtotal = 1h1xA1h1xA + LkxALkxA + 1h2xA
Identify the types of heat transfer models for heat transfer through the wall of a house if the air temperature in and outside the house remain constant.
Steady One-dimensional
Identify the true statements about Fourier's law of heat conduction.
The rate of heat transfer is directly proportional to the temperature difference. The rate of heat transfer is directly proportional to the thermal conductivity. The rate of heat transfer is inversely proportional to the length of heat conduction.
Identify the true statements about heat conduction through a wall if the air temperatures between the inner and outer surfaces of the walls of the house are the same.
There is no heat transfer through the wall from the top to the bottom. There is no heat transfer through the wall from left to right.
For two metal bodies in contact, identify the correct statements about thermal contact resistance.
Thermal contact resistance depends on the temperature. Thermal contact resistance depends on the material properties.
How do the thin plate fins of a car radiator increase the heat rate of the system?
They increase the surface area.
True or false: Fins with triangular and parabolic profiles are more efficient than fins with rectangular profiles.
True
True or false: The two assumptions used to solve multidimensional heat transfer problems by treating them as one-dimensional result in different resistance networks but close values of the total thermal resistance.
True
Identify the correct relation between the overall heat transfer coefficient (U)U and the total thermal resistance for a system (Rtotal)Rtotal. The area of heat transfer is given by A.
U = 1/A×Rtotal
If the fin tip is assumed to be adiabatic, the boundary condition at the fin tip can be expressed by the equation _____.
d(theta)/dx |x=L = 0
For a thermal system, identify the governing differential equation for one-dimensional fins with a constant cross section and constant thermal conductivity, where h is the heat transfer coefficient, k is the constant thermal conductivity, Ac is the constant cross-sectional area of the fin, p is the perimeter of the fin, x is the length of the fin, T is the temperature of the fin, and T∞ is the temperature of the surrounding fluid.
d2T/dx2 − (hp/kAc) (T − T∞) = 0
For a thermal system, identify the governing differential equation for one-dimensional fins with a constant cross section and constant thermal conductivity, where θ is the excess temperature (T - T∞), m2 = hpkAchpkAc, h is the heat transfer coefficient, k is the constant thermal conductivity, Ac is the constant cross sectional area of the fin, p is the perimeter of the fin, x is the length of the fin, T is the temperature of the fin, and T∞ is the temperature of the surrounding fluid.
d2θ/dx2 - m2θ = 0
Thermal contact resistance is observed to decrease with _____ surface roughness and _____ interface pressure.
decreasing; increasing
For a thermal system, in the governing differential equation d2θdx2d2θdx2 - m2θ = 0 for one-dimensional fins with a constant cross section and constant thermal conductivity, θ is the _____, where m2 = hpkAchpkAc, h is the heat transfer coefficient, k is the constant thermal conductivity, Ac is the constant cross sectional area of the fin, p is the perimeter of the fin.
excess temperature
If A is the area of the interface, Q˙interfaceQ˙interface is the rate of heat transfer through the interface, and ∆Tinterface∆Tinterface is temperature difference across the interface, the thermal contact conductance (hc)hc can be calculated using the formula ______.
hc = Q˙interface/A x ∆Tinterface
A hot aluminum rod is allowed to cool in air. The combined heat transfer coefficient (hcombined)hcombined for this model is given by _____, where hradhrad is the radiation heat transfer coefficient and hconvhconv is the convection heat transfer coefficient.
hrad + hconv
The unit of conduction resistance is _____.
kelvin(K)/watt(W)
For the cylindrical pipe shown in the figure, the critical radius of insulation (rcr, cylinder) can be calculated using the formula _____, where h is the heat transfer coefficient and k is the thermal conductivity.
rcr, cylinder = k/h
For the thermal network shown in the figure, the rate of steady heat transfer between two surfaces is equal to _____.
the total thermal resistance between those two surfaces divided by the temperature difference
The SI unit for rate of heat transfer (Q˙cond)(Q˙cond) is _____.
watt (W)
The unit of the radiation heat transfer coefficient (hrad)hrad is _____.
watt(meter)2kelvin
The unit for the overall heat transfer coefficient (U) for a system is _____.
watt/meter^2×kelvin
