Heat loss Give step-by-step calculation and explanationConsider a person sitting nude on a beach in Florida. On a sunny day, visible radiation energy from thesun is absorbed by the person at a rate of 30 kcal/h or 34.9 W. The air temperature is a warm 30 °C andthe individual’s skin temperature is 32 °C. The effective body surface exposed to the sun is 0.9 m².(Assume this same area for sun absorption, radiative transfer, and convective loss. Is this a goodassumption?)a. Find the net energy gain or loss from thermal radiation each hour. (Assume thermal radiativegain and loss according to the equation 6.51 in Herman and an emissivity of 1.) Answeer a 21kcal/hror 2YD-(4).Eguadion(6.51)- (40 Tin)Eskin Askin (Tskin – Troom)dt= (4 x 5.67 x 10¬8 w/m²–K*x (307 K)³)€skin Aşkin (Tskin – Troom) -(6.52)b. If there is a 4 m/s breeze, find the energy lost by convection each hour. (Use Eq. 6.61 with eq.6.63.) Àns48 kcal /hr or 24W1Equationh.(Tskin – Tair),(6.61)Adthe10.45 – w + 10w0.5(6.63)-c. If the individual’s metabolic rate is 80 kcal/h (93.0 W) and breathing accounts for a loss of 10kcal/h (11.6 W), how much additional heat must be lost by evaporation to keep the body coretemperature constant? Aas = 43 kcal/h or 50wd. How would you suggest that he loses this energy? Explain your answer clearly and convincingly.

Answered: Image /qna-images/answer/a8e5bd5b-8eab-42a4-9827-ed20c5325247.jpg

Consider a person sitting nude on a beach in Florida. On a sunny day, visible radiation energy from the sun is absorbed by the person at a rate of 30 kcal/h or 34.9 W. The air temperature is a warm 30 °C and the individual's skin temperature is 32 °C. The effective body surface exposed to the sun is 0.9 m². (Assume this same area for sun absorption, radiative transfer, and convective loss. Is this a good assumption?) a. Find the net energy gain or loss from thermal radiation each hour. (Assume thermal radiative gain and loss according to the equation 6.51 in Herman and an emissivity of 1.) Anseera 21kcal/hr or 24 -(). Eguadion (6.51) - (40Tin)Eskin Askin (Tskin – Troom) dt = (4 x 5.67 × 10-8 w/m²–Kª x (307 K)')eskin Aşkin (Tskin – Troom). (6.52) b. If there is a 4 m/s breeze, find the energy lost by convection each hour. (Use Eq. 6.61 with eq. 6.63.) Àns = 48 kcal/hr or 24W 1 (dQ Equation = h.(Tskin – Tair), (6.61) - - A dt he 10.45 – w + 10w" ,0.5 (6.63) c. If the individual's metabolic rate is 80 kcal/h (93.0 W) and breathing accounts for a loss of 10 kcal/h (11.6 W), how much additional heat must be lost by evaporation to keep the body core temperature constant? Ans = 43 kal/h or sow

Consider a person sitting nude on a beach in Florida. On a sunny day, visible radiation energy from the sun is absorbed by the person at a rate of 30 kcal/h or 34.9 W. The air temperature is a warm 30 °C and the individual's skin temperature is 32 °C. The effective body surface exposed to the sun is 0.9 m². (Assume this same area for sun absorption, radiative transfer, and convective loss. Is this a good assumption?) a. Find the net energy gain or loss from thermal radiation each hour. (Assume thermal radiative gain and loss according to the equation 6.51 in Herman and an emissivity of 1.) Anseera 21kcal/hr or 24 -(). Eguadion (6.51) - (40Tin)Eskin Askin (Tskin – Troom) dt = (4 x 5.67 × 10-8 w/m²–Kª x (307 K)')eskin Aşkin (Tskin – Troom). (6.52) b. If there is a 4 m/s breeze, find the energy lost by convection each hour. (Use Eq. 6.61 with eq. 6.63.) Àns = 48 kcal/hr or 24W 1 (dQ Equation = h.(Tskin – Tair), (6.61) - - A dt he 10.45 – w + 10w" ,0.5 (6.63) c. If the individual's metabolic rate is 80 kcal/h (93.0 W) and breathing accounts for a loss of 10 kcal/h (11.6 W), how much additional heat must be lost by evaporation to keep the body core temperature constant? Ans = 43 kal/h or sow

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter11: Heat Transfer By Radiation

Section: Chapter Questions

Problem 11.65P

See similar textbooks

Similar questions

Determine the rate of radiant heat emission in watts per square meter from a blackbody at (a) 15C, (b) 600C, and (c) 5700C.
Two large parallel plates with surface conditions approximating those of a blackbody are maintained at 816C and 260C, respectively. Determine the rate of heat transfer by radiation between the plates in W/m2 and the radiative heat transfer coefficient in W/m2K.
1.28 The sun has a radius of and approximates a blackbody with a surface temperature of about 5800 K. Calculate the total rate of radiation from the sun and the emitted radiation flux per square meter of surface area.
1.26 Repeat Problem 1.25 but assume that the surface of the storage vessel has an absorbance (equal to the emittance) of 0.1. Then determine the rate of evaporation of the liquid oxygen in kilograms per second and pounds per hour, assuming that convection can be neglected. The heat of vaporization of oxygen at –183°C is .
A long wire 0.7 mm in diameter with an emissivity of 0.9 is placed in a large quiescent air space at 270 K. If the wire is at 800 K, calculate the net rate of heat loss. Discuss your assumptions.
11.31 A large slab of steel 0.1 m thick contains a 0.1 -m-di- ameter circular hole whose axis is normal to the surface. Considering the sides of the hole to be black, specify the rate of radiative heat loss from the hole. The plate is at 811 K, and the surroundings are at 300 K.
11.41 Determine the steady-state temperatures of two radiation shields placed in the evacuated space between two infinite planes at temperatures of 555 K and 278 K. The emissivity of all surfaces is 0.8.
1.47 A flat roof is modeled as a flat plate insulated on the bottom and placed in the sunlight. If the radiant heat that the roof receives from the sun is , the convection heat transfer coefficient between the roof and the air is 12 W/m2 K, and the air temperature is , determine the roof temperature for the following two cases: (a) Radiative heat loss to space is negligible, (b) The roof is black and radiates to space, which is assumed to be a black- body at 0 K.
1.13 If the outer air temperature in Problem is –2°C, calculate the convection heat transfer coefficient between the outer surface of the window and the air, assuming radiation is negligible.