A person is found dead at 5PM in a room whose temperature is 20°C. The temperature of the body is measured to be 25°C when found, Modeling the body as a 30-cm-diameter, 1.70-m-long cylinder and the heat transfer coefficient estimated to be 8 W/m2·K. and using the lumped system analysis as a rough approximation, estimate the time of death of the person.

A person is found dead at 5PM in a room whose temperature is 20°C. The temperature of the body is measured to be 25°C when found, Modeling the body as a 30-cm-diameter, 1.70-m-long cylinder and the heat transfer coefficient estimated to be 8 W/m2·K. and using the lumped system analysis as a rough approximation, estimate the time of death of the person.

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.

Chapter3: Transient Heat Conduction

Section: Chapter Questions

Problem 3.16P: 3.16 A large, 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer...

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1.60 Two electric resistance heaters with a 20 cm length and a 2 cm diameter are inserted into a well-insulated 40-L tank of water that is initially at 300 K. If each heater dissipates 500 W, what is the time required for bringing the water temperature in the tank to 340 K? State your assumption for your analysis.
3.16 A large, 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer coefficient on one side is and on the other side is . If the temperature of both streams is suddenly changed from 38°C to 93°C, determine how long it takes for the copper plate to reach a temperature of 82°C.
1.19 A cryogenic fluid is stored in a 0.3-m-diameter spherical container is still air. If the convection heat transfer coefficient between the outer surface of the container and the air is 6.8 , the temperature of the air is 27°C, and the temperature of the surface of the sphere is –183°C, determine the rate of heat transfer by convection.
Ground turkey was made into me at balls and refrigerated at 2 ° C before being deep fried. The diameter of each meat ball is 9cm. To make sure that the meat balls are safe to be consumed, they must be cooked over 70 ° C. Assume that the cooking oil is at a constant temperature of 180 ° C and has a heat transfer coefficient of 50 W/(m 2 ∙ K). The conductivity and specific heat of the ground turkey are approximated at 2 W/( m∙K ) and 4 kJ/( kg ∙ K) respectively. The density of the ground turkey is 500kg/ m 3 . a) During the deep- frying process, do you anticipate that each meat ball has a uniform temperature distribution throughout its volume? Please show calculation to support your answer (5 pts) . b) Please calculate the minimum time required for cooking (1 5 p ts). c) When served, what are the surface and center temperatures of each meat ball ( 15 pts).
A person is found dead at 5 PM in a room whose temperature is 20 °C. The temperature of the body is measured to be 25 °C when found, and the heat transfer coefficient is estimated to be h 8 W/m2 °C. Modeling the body as a 30-cm-diameter, 1.70-m-long cylinder, estimate the time of death of that person. The body can be modeled as a 30 cm diameter, 1.70-m-long cylinder. The thermal properties and body temperature of 37 °C. let The average human body is 72 percent water by mass, and thus we can assume the body to have the properties of water at the average temperature of (37 + 25)/2 = 31 °C; k = 0.617 W/m · °C, p= 996 kg/m³, and Cp=4178 J/kg · °C
A pipe in a manufacturing plant is transporting superheated vapor at a mass flow rate of 0.3 kg/s. The pipe is 10 m long, has an inner diameter of 5 cm and pipe wall thickness of 6 mm. The pipe has a thermal conductivity of 17 W/m.K, and the inner pipe surface is at a uniform temperature of 120 °C. The temperature drop between the inlet and the exit of the pipe is 7 °C, and the constant pressure specific heat of vapor is 2190 J/kg.°C. If the air temperature in the manufacturing plant is 25°C, determine the heat transfer coefficient as a result if convection between the outer pipe surface and the surrounding air. T(r) = 120°C Superheated Air, 25°C r2 vapor r1 0.3 kg/s L = 10 m Tin-Tout = 7°C
A steel plate having a thickness of 100 mm is suddenly exposed to a hot gas at 1000 °C in a furnace. One surface of the plate is heated while the other surface of the plate can be approximated to be adiabatic. The initial temperature of the steel plate is 20 °C. The thermal conductivity and thermal diffusivity of the steel plate are 34.8 W/m K and 0.555 x 10-5 m²/s respectively. The convective heat-transfer coefficient is 174 W/m²K. a) Determine the time necessary to raise the surface temperature of the steel plate to 500 °C. b) Determine the maximum temperature difference in the cross-section of the steel plate at the time evaluated in part a) above. c) Determine the heat energy transferred to the steel plate per unit wall surface area by the time evaluated in part a) above.
A pipe 30 m long with an outer diameter of 75 mm is used to deliver steam at a rate of 2000 kg / hour. The vapor pressure is 198.53 kPa entering the pipe with a quality of 98%. The pipe needs to be insulated with a thermal conductivity of 0.2 W / (m K) so that the quality of the steam will only slightly decrease to 95%. The outer surface temperature of the insulation is assumed to be 25 ° C. Ignore resistance conductive of the pipe material and it is assumed that there is no pressure drop in the pipe. a. Determine the enthalpy of incoming vapor = AnswerkJ / kg. b. Determine the enthalpy of steam coming out = AnswerkJ / kg. c. Determine the vapor heat change / loss along the flow = Answerwatt. d. Specify the minimum required insulation thickness = Answercm.
A pipe 30 m long with an outer diameter of 75 mm is used to deliver steam at a rate of 1500 kg / hour. The vapor pressure is 198.53 kPa entering the pipe with a quality of 98%. The pipe needs to be insulated with a thermal conductivity of 0.2 W / (m K) so that the quality of the steam will only slightly decrease to 95%. The outer surface temperature of the insulation is assumed to be 25 ° C. Ignore resistance conductive of the pipe material and it is assumed that there is no pressure drop in the pipe. a. Determine the enthalpy of incoming vapor = Answer kJ / kg. b. Determine the enthalpy of steam coming out = Answer kJ / kg. c. Determine the vapor heat change / loss along the flow = Answer watt. d. Specify the minimum required insulation thickness = Answer cm.
Q2/ A 4-m-internal-diameter spherical tank made of 1.75-cm-thick stainless steel (k 15 W/m °C) is used to store iced water at 0°C. The tank is located in a room whose temperature is 35°C. The walls of the room are also at 35°C. The outer surface of the tank is black, and heat transfer between the outer surface of the tank and the surroundings is by natural convection and radiation. The convection heat transfer coefficients at the inner and the outer surfaces of the tank are 80 W/m2 °C and 10 W/m2· °C, respectively. Determine (a) the rate of heat transfer to the iced water in the tank and (b) the amount of ice at 0°C that melts during a l-h period. The heat of fusion of water at atmospheric pressure is hif 334 kJ/kg.
A pipe 30 m long with an outer diameter of 75 mm is used to carry steam at a rate of 1000 kg / hour. The vapor pressure is 198.53 kPa entering the pipe with a quality of 98%. The pipe needs to be insulated with a thermal conductivity of 0.2 W / (m K) so that the quality of the steam will only slightly decrease to 95%. The outer surface temperature of the insulation is assumed to be 25 ° C. Ignore resistance conductive of the pipe material and it is assumed that there is no pressure drop in the pipe. a. Determine the enthalpy of incoming vapor = Answer kJ / kg. b. Determine the enthalpy of steam coming out = Answer kJ / kg. c. Determine the vapor heat change / loss along the flow = Answer watt. d. Specify the minimum required insulation thickness = Answer cm.
A steel plate having a thickness of 100 mm is suddenly exposed to a hot gas at 1000 oC in a furnace. One surface of the plate is heated while the other surface of the plate can be approximated to be adiabatic. The initial temperature of the steel plate is 20 oC. The thermal conductivity and thermal diffusivity of the steel plate are 34.8 W/m K and 0.555 x 10-5 m2 /s respectively. The convective heat-transfer coefficient is 174 W/m2 K. a) Determine the time necessary to raise the surface temperature of the steel plate to 500 oC. b) Determine the maximum temperature difference in the cross-section of the steel plate at the time evaluated in part a) above. c) Determine the heat energy transferred to the steel plate per unit wall surface area by the time evaluated in part a) above. Use the conduction charts