(a) Explanation Given: Temperature of Lava is 1200 ° C . Temperature of ground initially is 15 ° C . Convective heat transfer coefficient of Lava is 3500 W / m 2 ⋅ K . Time is 2s . Concept used: Consider the properties of the ground as same as of the properties of Dry soil. Write the expression for the thermal diffusivity of the ground. α = k ρ C p ....... (1) Here, α is the thermal diffusivity, k is the thermal conductivity of the ground, ρ is the density of soil and C p is the heat capacity of the soil. Write the expression for surface temperature of the ground. T s − T i T ∞ − T i = e r f c ( x 2 α t ) − exp ( h 2 α t k 2 ) e r f c ( h α t k ) ....... (2) Here, T s is the surrounding temperature, T i is the initial temperature of the ground, T ∞ is the surrounding temperature, T s is the surface temperature and t is the time required for heat flux transfer. Obtain the Properties of Dry soil from appendix table A-8 “Properties of miscellaneous material” as ρ = 1500 kg / m 3 , C p = 1900 J / kg ⋅ K and k = 1.0 W / m ⋅ K . Calculation: Substitute 1500 kg / m 3 for ρ , 1900 J / kg ⋅ K for C p and 1.0 W / m ⋅ K for k in equation (1). α = ( 1 ) 1500 ( 1900 ) = 3.509 × 10 − 7 m 2 / s Substitute 1200 ° C for T ∞ , 15 ° C for T i , 3 (b) To determine The heat Flux after 2s of flow of lava over it.

6th Edition

ISBN: 9781260699326

Author: CENGEL

Publisher: MCG

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Question

Chapter 4, Problem 157P

(a)

To determine

The temperature of ground surface after 2 seconds.

(b)

To determine

The heat Flux after 2s of flow of lava over it.

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Chapter 4, Problem 156P

Chapter 4, Problem 158P

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Chapter 4 Solutions

HEAT+MASS TRANSFER:FUND..(LL)-W/CONNECT

Ch. 4 - What is the physical significance of the Biot...Ch. 4 - What is lumped system analysis? When is it...Ch. 4 - In what medium is the lumped system analysis more...Ch. 4 - For which solid is the lumped system analysis more...Ch. 4 - For which kinds of bodies made of the same...Ch. 4 - Consider heat transfer between two identical hot...Ch. 4 - Consider heat transfer between two identical hot...Ch. 4 - Consider a hot baked potato on a plate. The...Ch. 4 - Consider a potato being baked in an oven that is...Ch. 4 - Consider two identical 4-kg pieces of roast beef....

Ch. 4 - Consider a sphere and a cylinder of equal volume...Ch. 4 - Obtain relations for the characteristic lengths of...Ch. 4 - Obtain a relation for the time required for a...Ch. 4 - A brick of 20310257mm in dimension is being burned...Ch. 4 - Prob. 15P Ch. 4 - Prob. 16P Ch. 4 - Prob. 17P Ch. 4 - Metal plates...Ch. 4 - Prob. 19P Ch. 4 - Prob. 20P Ch. 4 - Prob. 21P Ch. 4 - A 6-mm-thick stainless steel strip...Ch. 4 - After heat treatment, the 2-cm-thick metal plates...Ch. 4 - A long copper rod of diameter 2.0 cm is initially...Ch. 4 - Prob. 25P Ch. 4 - Steel rods...Ch. 4 - Prob. 27P Ch. 4 - Prob. 28P Ch. 4 - To warm up some milk for a baby, a mother pours...Ch. 4 - A person is found dead at 5 p.m. in a room whose...Ch. 4 - Prob. 31P Ch. 4 - In an experiment, the temperature of a hot gas...Ch. 4 - Prob. 33P Ch. 4 - Pulverized coal particles are used in oxy-fuel...Ch. 4 - Oxy-fuel combustion power plants use pulverized...Ch. 4 - Plasma spraying is a process used for coating a...Ch. 4 - Consider a spherical shell satellite with outer...Ch. 4 - Prob. 38P Ch. 4 - Prob. 39P Ch. 4 - Prob. 40EP Ch. 4 - Consider a sphere of diameter 5 cm, a cube of side...Ch. 4 - Prob. 42P Ch. 4 - An egg is to be cooked to a certain level of...Ch. 4 - What is an infinitely long cylinder? When is it...Ch. 4 - What is the physical significance of the Fourier...Ch. 4 - Prob. 46CP Ch. 4 - Prob. 47CP Ch. 4 - The Biot number during a heat transfer process...Ch. 4 - A body at an initial temperature of Ti, is brought...Ch. 4 - Prob. 50P Ch. 4 - In a meat processing plant, 2-cm-thick steaks...Ch. 4 - Prob. 52P Ch. 4 - Prob. 53P Ch. 4 - Prob. 54P Ch. 4 - Prob. 55P Ch. 4 - Layers of 23-cm-thick meat slabs...Ch. 4 - Prob. 57P Ch. 4 - Prob. 58P Ch. 4 - Prob. 59P Ch. 4 - Prob. 60P Ch. 4 - Prob. 61P Ch. 4 - Prob. 62EP Ch. 4 - Prob. 63P Ch. 4 - Prob. 64P Ch. 4 - Prob. 65P Ch. 4 - Prob. 66P Ch. 4 - A 30-cm-diameter, 4-m-high cylindrical column of a...Ch. 4 - Prob. 68P Ch. 4 - Prob. 69P Ch. 4 - Prob. 70P Ch. 4 - For heat transfer purposes, an egg can be...Ch. 4 - Citrus fruits are very susceptible to cold...Ch. 4 - Chickens with an average mass of 1.7 kg...Ch. 4 - Prob. 74P Ch. 4 - Prob. 75P Ch. 4 - Prob. 76P Ch. 4 - Oranges of 2.5-in-diameter...Ch. 4 - Prob. 78P Ch. 4 - Prob. 79P Ch. 4 - Prob. 80P Ch. 4 - Prob. 81P Ch. 4 - A 9-cm-diameter potato...Ch. 4 - In Betty Crocker s Cookbook, it is stated that it...Ch. 4 - Prob. 84P Ch. 4 - Under what conditions can a plane wall be treated...Ch. 4 - What is a semi-infinite medium? 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How is it...Ch. 4 - How is the product solution used to determine the...Ch. 4 - Prob. 109CP Ch. 4 - Consider a short cylinder whose top and bottom...Ch. 4 - Prob. 111P Ch. 4 - Prob. 112P Ch. 4 - Prob. 113P Ch. 4 - A hot dog can be considered to be a cylinder 5 in...Ch. 4 - Prob. 115P Ch. 4 - Prob. 116P Ch. 4 - A 2-cm-high cylindrical ice block...Ch. 4 - Prob. 118P Ch. 4 - Prob. 119P Ch. 4 - Prob. 120P Ch. 4 - Prob. 121P Ch. 4 - Prob. 122P Ch. 4 - Prob. 123P Ch. 4 - Prob. 124CP Ch. 4 - How does refrigeration prevent or delay the...Ch. 4 - What are the environmental factors that affect the...Ch. 4 - What is the effect of cooking on the...Ch. 4 - Prob. 128CP Ch. 4 - Prob. 129CP Ch. 4 - Prob. 130CP Ch. 4 - Prob. 131CP Ch. 4 - How does the rate of freezing affect the...Ch. 4 - Prob. 133CP Ch. 4 - Prob. 134CP Ch. 4 - Prob. 135CP Ch. 4 - Prob. 136CP Ch. 4 - Prob. 137CP Ch. 4 - Prob. 138P Ch. 4 - Chickens with an average mass of 2.2 kg and...Ch. 4 - Prob. 140EP Ch. 4 - Prob. 141P Ch. 4 - Prob. 142P Ch. 4 - A long roll of 2-m-wide and 0.5-cm-thick 1-Mn...Ch. 4 - Prob. 144P Ch. 4 - Prob. 145P Ch. 4 - Prob. 146P Ch. 4 - During a picnic on a hot summer day, the only...Ch. 4 - Two metal rods are being heated in an oven with...Ch. 4 - Stainless steel ball bearings...Ch. 4 - Prob. 150P Ch. 4 - Prob. 151P Ch. 4 - In Betty crockers Cookbook, it is stated that it...Ch. 4 - A watermelon initially at 35C is to be cooled by...Ch. 4 - Prob. 154P Ch. 4 - Prob. 155P Ch. 4 - Prob. 156P Ch. 4 - Prob. 157P Ch. 4 - Prob. 158P Ch. 4 - Prob. 159P Ch. 4 - Prob. 160P Ch. 4 - Prob. 161P Ch. 4 - Prob. 162P Ch. 4 - Prob. 163P Ch. 4 - Lumped system analysis of transient heat...Ch. 4 - Prob. 165P Ch. 4 - Prob. 166P Ch. 4 - An 18-cm-long, 16-cm-wide, and 12-cm-high hot iron...Ch. 4 - Prob. 168P Ch. 4 - Prob. 169P Ch. 4 - Prob. 170P Ch. 4 - Prob. 171P Ch. 4 - Prob. 172P Ch. 4 - A long 18-cm-diameter bar made of hardwood...Ch. 4 - Consider a 7.6-cm-long and 3-cm-diameter...Ch. 4 - Consider a 7.6-cm-diameter cylindrical lamb meat...Ch. 4 - Prob. 176P Ch. 4 - A small chicken (k=0.45W/m.K,=0.1510-6m2/s) and...Ch. 4 - A potato may be approximated as a 5.7-cm-diameter...Ch. 4 - When water, as in a pond or lake, is heated by...Ch. 4 - A large chunk of tissue at 35C with a thermal...Ch. 4 - Prob. 181P Ch. 4 - Citrus trees are very susceptible to cold weather,...

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