Heat flow Definition and 104 Threads

I'm really not sure, have I gone through the right process here? I didn't actually finish the calculation, I'm just curious about the process.

EDIT: Typo, the Z' should be Z''

What effects would having 2-3 times the current heat flow of the Earth have had in the past? Would this have had a significant effect on global temperatures?

Homework Statement There are two tanks with water, there are standing very close to each other. Tank 1 is having a temperature of 0 degrees and tank 2 is having a temperature of 10 degrees. The heatflow between the two is Q1. Then tank two is getting a temperature of 100 degrees. That heatflow...

Homework Statement The brick wall of a building has dimensions of 4m by 10m, it is 15cm thick with a coefficient of thermal conductivity of 0.8 (Wm^-1C^-1). (a) How much heat flows through the wall in a 12-hour period when the average inside temperature is 20 C and the average outside...

Homework Statement The temperatur at the point (x,y,z) in a substance with conductivity K=6.5 is u(x,y,z)=2y2+2z2. Find the rate of heat flow inward across the cylindrical surface y2+z2=6, 0≤x≤4. Homework Equations F=-k∇u -k∫∫s∇u*ds The Attempt at a Solution So F=-6.5(0,4y,4z) I...

Hi all, I have a mostly theoretical question here. I have a copper rod approximately 2cm in diameter and 3cm tall. It is fit snugly inside a much taller cylinder. Heat enters through the base of the copper rod and exits through the sides into the tall cylinder. I need to improve conduction...

In my book it says: The bigger entropy of a system, the more heat from the surroundings can enter it. Now, I don't really understand why that is completely. Can anyone explain me? - both in terms of the actual thermodynamic formulas (thermodynamic identity etc.) and in terms of multiplicity...

In my book it says: The bigger entropy of a system, the more heat from the surroundings can enter it. Now, I don't really understand why that is completely. Can anyone explain me? - both in terms of the actual thermodynamic formulas (thermodynamic identity etc.) and in terms of multiplicity?

why does heat flows from a high temperature body to a low temperature body? The above statement can be concluded from applying conservation of momentum to particles of a system containing a high and low temperature bodies. But in texts, its written that the above statement is a consequence of...

Homework Statement n is given by: ∂2Θ/∂x2=1/α2 ∂Θ/∂t , where Θ(x, t) is the temperature as a function of time and position, and α2 is a constant characteristic for the material through which the heat is flowing. We have a plate of infinite area and thickness d that has a uniform...

Homework Statement You are polishing a 10.0 g gold ring. (treat as an ideal solid). After doing this for a minute, you find that the ring is hot, having increased the temperature by 15 deg C. Calculate the heat that flows into or out of the system and specify which direction. Homework...

Hello With what velocity does heat flow in solids? What are the factors on which its velocity depends? Thnx

Homework Statement Three rods of identical cross-sectional area are made from the same metal, form the sides of an isosceles triangle ABC right angled at B. The points A and B are maintained at temperature T and √2 T respectively in steady state. Assume that only heat conduction takes place...

Homework Statement Consider a rubber band for which the tension, f, as a function of temperature T and length L is f = \kappa T (L+\gamma L^2), where \kappa and \gamma are positive constants. Determine the heat flow between it and its surroundings when the rubber band is stretched reversibly...

Homework Statement There is a wall 100 mm thick, find the U-value. Then a plasterboard lining is added of thickness x and a gap between it and the wall of 20 mm wall thickness b=0.1m, thermal conductivity \kappa_1=0.5 W m^{-1} K^{-1} plasterboard thickness xm, thermal conductivity \kappa_2=0.1...

Homework Statement a bushwalker wears clothing that is 2.0cm thick with a surface area of 1.9m^2. The material has k = 0.042 WM^-1K^-1. Her skin temperature is 33 degrees C and the ambient temp. is 0 degrees C. Calculate rate of heat loss through her clothing while she is sitting...

Homework Statement A block of material with a cross sectional area of 15cm^2 and length of 8cm is at hand. A temperature difference of 30degrees is established and maintained across the block. Find the rate of heat flow through it if the material is wood (K = 0.08Js-1m-1C-1) Homework...

HI I would like to test the thermal conductivity of r wall by K=Q*d/ A (t2-t1) K =conductivity d+=thickness A= area Q= heat flow my problem how I could simulate heat in my experiment and how I will measure the heat flow? could you please help me. Kind regards

I'm trying to understand how to set up the problem of a 1D wire that is insulated at one end and has a heat source at the other. I know the heat law, from my textbook: du/dt = B d2u/dx2 + q(x,t) 0 < x < L, t > 0 Where q(x,t) is the source of heat. The problem is, I want the heat...

Homework Statement A styrofoam cooler (k = 0.030 W/(m·°C) has outside dimensions of 0.190 m × 0.210 m × 0.340 m, and an average thickness of 2.2 cm. How long will it take for 3.60 kg of ice at 0°C to melt in the cooler if the outside temperature is 26.0°C? Homework Equations Delta Q /...

Homework Statement The plane region defined by \[A = \left\{ {(x,y)/0 < x < 1,0 < y < \infty } \right\}\] defines the profile of a semi infinite wall, where there's a stationary regime heat flow. The left and right sides are isolated at 15º, and the base is isolated at 0º. Find T(x,y) in...

Homework Statement Two bodies of temperature T and T+\DeltaT respectively (where \DeltaT>0) are brought into direct thermal contact. Use a mathematical formulation of the second law to show: (i)Which way heat flows; is this heat flow reversible? Homework Equations 2nd law of...

Homework Statement The absolute value of the heat flow rate through a slab of area 0.83 m2 is 240 W. The thickness of the slab is 1.4 cm and its thermal conductivity is 0.6 W/(m·K). If the hot surface of the slab is at 40°C find the temperature of the cold surface. Homework Equations...

Homework Statement The ceiling of a room has an area of 135ft^2. The ceiling is insulated to an R value of 30 (in units of ft^2*deg. F*h/Btu). The surface in the room is maintained at 63 deg. F, and the surface in the attic has a temperature of 38 deg. F. What is the heat flow through the...

Homework Statement Bob who is working on a glacier wants to experiment with heat and has constructed a two part metal rod. The left rod is silver and has length L1 = .5454 M, and has a cross sectional area A = 3.1416 CM^2. It is joined end to end with a lead rod of identical diameter and...

Homework Statement The temperature u in a star of conductivity 6 is inversely proportional to the distance from the center: u = \frac{3}{\sqrt{x^{2} + y^{2} + z^{2}}} If the star is a sphere of radius 3, find the rate of heat flow outward across the surface of the star. Homework...

Homework Statement Find a formal solution to the given initial boundary value problem. du/dt=5(d^2u/dx^2) 0<x<1 t>0 u(0,t)=u(1,t)=0 t>0 u(x,0)=(1-x)(x^2) 0<x<1 Homework Equations 1) u(x,t) = a0/2 + sum[an*e^(-b(n pi/L)^2*t) * cos(n pi x/L) 2) Fourier series equation...

If an object receives heat from a heat reservoir, is it necessary for the heat receiver to release heat? Can the heat receiver increase its internal energy without heat flow out of the receiver? And what happens when the system between heat provider and heat receiver reaches a steady state...

I have been wondering, does specific heat capacity affect the rate of heat flow from one substance to another? For example if the substances at heated up to the same temperature then left outside until thermal equilibrium is reached. I would think the one with the larger specific heat...

1. Problem: derive the energy balance from first principles of a hoop of inner radius ri, outer radius ro. the hoop material has a density of rho (p), heat capacity of c and thermal conductivity k. the center of the hoop has a temperature of T1 and the gas inside the hoop has a convection...

Homework Statement Two rooms, each a cube 3.8 m on a side, share a 12 cm thick brick wall. Because of a number of 100 W light-bulbs in one room, the air is at 27°C, while in the other room it is at 10°C. How many of the 100 W light-bulbs are needed to maintain the temperature difference...

Homework Statement Two containers contain molecules at different temperatures as shown. They are allowed to exchange heat between them, but not with outside. Which of the following statements is most accurate? a) Container #1 looses Internal energy, container #2 gains internal energy b)...

I'm looking at project investigating thermal dissiplation around circular and square concrete piles, resting in a homogeneous material (soil) using two-dimensional finite element analysis. I'm applying a transient thermal loading cycle to the centre of the concrete pile over a 7-day test...

Homework Statement A heat engine follows the cycle shown in the figure. a) How much net work is done by the engine in one cycle? b) what is the heat flow into the engine per cycle? Diagram: http://farm4.static.flickr.com/3050/2703330973_26acb35c27.jpg?v=0 Homework Equations W =...

A long rod, insulated to prevent heat loss along its sides, is in perfect thermal contact with boiling water (at atmospheric pressure) at one end and with an ice-water mixture at the other View Figure . The rod consists of 1.00-m section of copper (one end in steam) joined end-to-end to a length...

Homework Statement Heat is allowed to flow out of an ideal gas at constant volume so that its pressure drops from PA = 2.9 atm to 1.4 atm. Then the gas expands at constant pressure, from a volume of 6.8 L to VC = 14.1 L where the temperature reaches its original value. See Fig. 15-27...

Homework Statement A steel bar 10cm long is welded end-to-end to a copper bar 20cm long. Both bars are insulated perfectly along their sides. Each bar has a radius of 2.0cm. The free end of the steel bar is maintained at 100 degrees C and the free end of the copper bar is maintained at 0...

"Proof" of heat flow direction? Hi everyone, I have a homework problem that basically says to prove that heat is conducted from a high temperature area to a low temperature area: Homework Statement Consider a one-dimensional conductor, stretching from x=0 to x=L. The two ends are...

Hi: I need some assistance or feedback on a Matlab program that I working on by applying the method of finite difference to calculate and output the steady state space distribution of temperature and resulting rate of hear flow in an I Beam made of Duralumin. I have written a partial code...

Homework Statement If temperature T in a solid is constant over any x,y plane show that the temperature and heat flow Q normal to x,y planes both satisfy the equation: del^2 T=D dT/dt where D is a constant. How would you expect the differential equations to be modified if it were necessary...

Could anyone gives me some hints of how to solve these problems ? 1. a sample of Ge has both electrons and holes carrying the current. When a hall measurement is done, there's no hall effect. If the mobility of electrons in Germanium is 3500 cm^2/V.s and that of holes is 1500 cm^2/V.s, show...

Homework Statement a person with a body temp of 37 degrees stands on snow with a temp of 0 degrees each of there shoes has a sole 1cm thick with an area of 300cm^2 and a 0.2 thermal conductivity what is the magnitude and direction of heat flow Homework Equations The Attempt at...

I have got a heat flow partial differential equation problem that is giving me a little problem due to the direction the temperature is changing. I have a bar (which lies along the X axis) which is initially at a uniform temperature which (for simplicity sake) we will call zero degrees. At...

Homework Statement Three identical rods are welded together to form a Y-shaped figure. The cross-sectional area of each rod is A, and they have length L and thermal conductivity k. View Figure The free end of rod 1 is maintained at T_1 and the free ends of rods 2 and 3 are maintained at a...

Hey everyone... I think I am not picking up on something here... The rate of heat flow across a slab is: P = (k*A*T)/D where k is the thermal conductivity of the medium, A is the cross sectional medium and T is the temperature...

I have derived expression for the heat flow along a bar with cross-sectional area A, given by 'Q = -KA dT/dx' where K is thermal conductivity constant and T and x refer to temperature and distance measured from the high temperature end of the bar. I understand this. My problem is when I try...

A wall is composed of two materials. Material 1 has a thickness of 7.21 cm and a thermal conductivity of 0.1 while material 2 has a thickness of 6.57 cm and a conductivity of 1. If the temperature difference inside to outside is 25 Co and the wall has an area of 10 m2, what is the energy loss...

The question gives a picture of a brayton cycle with temperature on the x-axis and pressure on the y-axis. It is for the monatomic gas, helium, and we are told that there are two moles. The diagram consists of two adiabatic processes and two isobaris processes. You are given two temparatures...

I have a question I'm trying to but I don't really know where to start. It is kind of an add-on to a previous question that I got pretty easliy. This is the first question: The answer to that was 156000 W. Now the second question asks how much heat must be supplied to raise the temperature and...