Heat transfer Definition and 875 Threads

Hi, I am studying the heat transfer in a stirling engine. The basic situation is a pipe blocked off at both ends, with air inside, and a displacer also inside, that moves backwards and forwards inside. It is not tight against the walls of the pipe, and air can pass around it. One end of...

Homework Statement A 4-in.-OD pipe is used to transport liquid metals and will have an outside surface temperature of 1400 F under operating conditions. Insulation 6-in. thick and having a thermal conductivity expressed as k = 0.08(1-0.0003T) where k is in [Btu/hr*ft*F] and T is in [F], is...

A student produces heat with a rate of 100W. How much heat is transferred from 90 students to a classroom in 50 minutes? Attempt at solution: 100W (100 J/s) * 90 students * 3000 seconds = 2,7 * 10^7 J. Does this make sense? The classroom is 3200 cubic meters and the air in it has a...

Ok it's my first time here and I was hoping to get some help on some questions I have been given. I am a first year chem eng and I'm finding the work pretty hard so any help at all will be useful, thanks. I need to find the convective heat transfer coefficient, h for petrol using this...

Homework Statement For the equation mc\DeltaT, i suppose \DeltaT should be Tf - Ti. However, at what condition we should let \DeltaT be Ti - Tf? I did come across a question which requires \DeltaT be Ti - Tf for a heat lost by an object. eg, heat lost by copper = heat absorbed by...

Homework Statement A tent being considered for cold-weather conditions has insulation on the top and sides with a conductivity, k = 0.040 W/(m*K) and a thickness, l = 0.50 cm. The tent (and surrounding medium) has the following conditions: a heater (inside the tent) producing heat at a rate...

Homework Statement http://img94.imageshack.us/img94/7101/45580214.jpg The Attempt at a Solution I'm trying to see if anyone will give me pointers on how to complete this assignment; because the professor is not helpful...at all.

Hi everyone. I am starting using Comsol modeling the temperature field of a buried cable installed into a PVC duct (2D problem). I have already solved the problem considering heat transfer by conduction. To do this, I have used the Electro-Thermal Interaction Application Mode (Perpendicular...

Hello, I hope this is the right place. Which of the following is false? a. Convection only takes place in gases and fluids. b. Heat radiation can take place across a vacuum. c. A perfect radiating surface has an emissivity (e) = 1. d. A perfect heat insulator has an...

Hey everyone, I'm new to the forums here and just have a question. Homework Statement A piston-cylinder device contains a mixture of .2kg of H2 and 1.6kg of N2 at 100kPa and 300K. Heat is now transferred to the mixture at constant pressure until the volume is doubled. Assuming constant...

Hi there, first of all: This is not a homework task or something like that. It is just one of my interests and I want you to check my calculation, if my thoughts are correct or not. Furthermore I apologize for my incorrect englisch but I am a foreigner. Okay, now some background...

What is the effect of different tube material (conductivity) on the heat transfer from water in an infinite tube to a surrounding infinite solid? The actual practical application is transfer of heat from hot water (~180F) in 3/4" tubes into sand for heat storage (and then the transfer back)...

l have a tube. and air enters the tube at a certain temparature and pressure. the air is threated as an ideal gas. Also, we know the exit pressure of the gas. In additon to those, we know radious of the tube.. How do we find the heat transfer rate.?

Homework Statement I have a cylinder that's made up of three sections, brass, stainless steel, brass. There's a heat source at the top and a heat sink at the bottom. I know the overall heat transfer coefficient, power supplied to the heater, length, diameter, cross-sectional area of the...

Homework Statement How much Fe at 200.0C must be placed in 100.00g of water at 20C so that the temperature of both will be at 35.0? Homework Equations Q=MCdeltaT The Attempt at a Solution Energy required to raise water is 6300 J So I did by: (keep in mind I used sig figs)...

Sorry for the long post but I could use some help. I am having a problem with a professor in my heat transfer class and I was wondering if anyone could help. Before I go on, I am not looking to get points back on my test, I only lost 2 so I don't care, I just want to know whether I am right...

I am trying to solve an advanced heat transfer problem and I have a 2nd order ODE. I can solve the homogeneous solution easily, but I am having trouble with the non-homogeneous solution.Homework Statement Given a turbine blade and asked to model as a one-dimensional fin, subject to the...

Homework Statement We're currently studying steady state one dimensional conduction heat transfer. We've touched on some surface convection, resistances in layers and fins. I don't think I'll have much issue with this problem once I find this out: What is a thermal driving force?

Greetings, I'm trying to design a system that creates a thermal gradient in 2 dimensions through several layers of very different material (copper, acrylic, and ice). I was wondering if there's some cheap software available or even some kind of shareware out there that could give me at least...

Homework Statement A nail driven into a board increases in temperature. Homework Equations If we assume that 60 % of the kinetic energy delivered by a 1.80-\rm kg hammer with a speed of 7.80 \rm m/s is transformed into heat that flows into the nail and does not flow out, what is the...

I'm super confused about this problem. I don't even know where to start. It seems very simple, but I just can't figure it out.. An electrical resistor is connected to a battery. After a brief transient, the resistor assumes a nearly uniform, steady-state temperature of 95 degrees C, while the...

hi this is my first post on this forums hope every would help me here on this question Homework Statement outside vertical tube = 1m outside diameter = 80mm exposed to saturated steam at atmosspharic preasure & is maintaiined at 50 c by the flow of cool water through the tube. Rate...

Please help me with this : 1) Water circulates throughout a house in a hotwater heating system. The water is pumped at a speed of .7 m/s through a 4 cm diameter pipe in the basement under a pressure of 3 atm. What is the pressure, to the nearest N/m^2, in a 2 cm pipe on the second floor 5...

Homework Statement Two rooms, each a cube 4.0m on a side, sare a 12cm thick brick wall. Because of a number of 100-W light-bulbs in one room the air is at 30 Celsius, while in the other room it is at 10 Celsius. How many of the 100-W light-bulbs are needed to maintain the temperature...

Homework Statement I am trying to get the units to match up on both sides. \frac{\partial T}{\partial t} = \frac{\nabla ^{2} T}{k} = \frac{1}{K}(\frac{\partial ^2 T}{\partial x^2} + \frac{\partial ^2 T}{\partial y^2} + \frac{\partial ^2 T}{\partial z^2}}), where k is the thermal resistivity...

I have a simplified model (see attached picture) which is part of a bigger model but for now the problem is as follows. I have a electropolished metal sheet which has spots on it which act as heat sinks because they are kept at constant temperature of 100K. The sheet is at room temperature...

I am trying to calculate the length of a pipe needed for an air cooling system I have found the following formulas: R=1/(h*a) where h is the convection coefficient and a is the surface area. h=Nu*(k/L) where Nu is the nusult number and k is the thermal conductivity. a=π*d*L where d is the...

This should be a fairly easy problem, although my Heat Transfer is quite rusty. I'm trying to get a ballpark estimate for a rotating cylinder that has flow on both the inside and outside. I know the temperature of the air at the inlet and outlet and am trying to get a decent estimation for...

I have a problem where the coefficient of thermal conductivity changes as temperature changes. Where/how do I input this into comsol?

Homework Statement (a) A 0.5kg mass of copper (specific heat 385 J kg-1K-1) at 600K is plunged into a litre of water at 20C. What is the equilibrium temperature, T2, of the system? What is the change in entropy of the water? (b) A litre of water is heated slowly at a constant rate from 20C...

Hi Everyone, I'm using Comsol v.3.4 to model a 1-meter copper rod experiencing a Temperature change of 294 Kelvin (4K at bottom and 300K at top). I have a slow computer/connection to the server, so I can't see any 3-D images or the Temperature plots. I'm working in the axial symmetry (2-D)...

Hi everyone... I am doing a problem on heat transfer on multilayers... want to find out the emmisivity of some materials like silicon, silicon dioxide, Nickel, Tungten... Can anyone suggest me some papers or links or good books to get the emmisivty of these materials... Thanks in advance

0„2When one steps from a shower on a cold morning, why doesthe tile floor seem so much colder than the air?

y Could some one please help me. My professor for a lower level programming class (in labview) has given the class the following assignment. This is not a heat transfer class and he has not spoken/taugh us anything related to heat transfer. He emailed us a few pages from a heat transfer...

Homework Statement A piece of metal with a mass of 1.50 kg, specific heat of 200 J/kg*oC, and initial temperature of 100oC is dropped into an insulated jar that contains liquid with a mass of 3.00 kg, specific heat of 1,000 J/kg*oC, and initial temperature of 0oC. The piece of metal is...

Homework Statement A plane wall of 152 mm thickness has surface area of 2.32 m2. One side of the wall is kept at 82.2 oC, and the other side at 4.4 oC. The thermal conductivity of the wall material is 0.036 W/m.K at 0 oC, and that at 93.3 oC is 0.055 W/m.K. Calculate the rate of heat...

Homework Statement I am working on a Matlab code that will solve a temperature grid for a 2D transient heat transfer problem. The code seemed to be working well but when I changed the timestep (to find timestep independance) I noticed that the larger the timestep, over the same duration, the...

what is the measurement for describing heat transfer rate if i know the specific heat of the objects? as example, i want to know if the heat transfer rate of a hot copper block attached to a block of room temp aluminum is different than same hot copper attached to a block of gold at room temp...

Homework Statement The pressure on 0.01 litres of mercury is increased reversibly and isothermally from zero to 1000 atm at room temperature (293 K). Mercury has a coefficient of volume expansion β = 1.82 × 10−4 K−1 , and an isothermal compressibility κT = 4.02 × 10−11 Pa−1 . Note: 1...

Homework Statement If 4.0 g of boiling water at 100.0°C was splashed onto a burn victim’s skin, and if it cooled to 45.0°C on the 37.0°C skin, (a) how much heat is given up by the water? (b) How much tissue mass, originally at 37.0°C, was involved in cooling the water? Homework Equations...

Please can someone show me how to work out the following questions. 1) A hot water cylinder holds 500 litres. If the primary heat source is 30kW and the supply water inlet to the cylinder is 12°C, how long will it take to heat the whole tank to 60°C? 2) The primary side of a plate heat...

Homework Statement One day Susan collected the mercury from the thermometers around her house and found she had 3.50 cubic centimeters of mercury (density= 13.6 g/cm^3) at room temperature of 28C. She places the mercury in a small bag and drops it into liquid nitrogen (-196C).a. Calculate how...

Homework Statement Heat is transferred into saturated liquid water until it is saturated vapor. The water remains at 300 C throughout the process. a. What is the initial pressure? b. What is the final pressure? c. How much heat is transferred per kg of water? I'm having trouble...

Homework Statement Estimate how long it should take to bring a cup of water to boiling temperature in a typical 600 watt microwave oven, assuming all energy ends up in the water(assume any reasonable initial temperature for the water.) What can you conclude about the amount of heat added...

I want to calculate the temperature on the outside of a pipe which has a heated fluid flowing through it. If I know the temperature of the fluid and the ambient temperature, as well as all the material properties such as thermal conductivity and convective heat transfer coefficient, is there a...

What is "heat transfer coefficient" What is heat transfer coefficient? and where can i find a table listing it?

There are two insulated compartments separated by a thin wall. The left side contains .060 mol of He at a initial temperature of 600 k and the right side contains .030 mol He at the initial temperature of 300 K. The compartment on the right is attached to a vertical cylinder, above which the...

What force is responsible for the phenomenon of heat transfer?

compressed gas...and heat transfer... If you were to take a cylinder of air, at room temp, and let's say it is 100ml in volume. If you were to take this cylinder of air, compress its volume to half its size, how much heat would that create (btu's) and if the heat were to dissipate, would the...

How many days does it take for a perfect black-body cube (0.0100 m on a side, 30 degrees C) to radiate the same amount of energy that a one-hundred-watt light bulb uses in one hour? If someone could point me in the right direction with how to go about solving this problem i would greatly...