Heat transfer Definition and 947 Threads

Hi there, I have this complicated question and I am not sure that I am converting everything corectly. The question is: "For conduction, the rate of heat transfer is given by \DeltaQ/\Deltat=-kA(\DeltaT/\Deltax) Data given is: k=806 W.m^-1.K^-1 A=2.53m^2 \DeltaT=-54.6^{}0C...

Hey everyone, I've got a finned surface question I've got a finned wall is constructed of aluminium alloy with k = 150 W/mK. The wall thickness is 2.0 mm and the fins, with a thickness of 2.0 mm, are straight with rectangular profile. The inside of the wall is maintained at a constant...

Homework Statement A 1.5-m^2 black surface at 120 degrees C is losing heat to the surrounding air at 30 degrees C by convection with a convection heat transfer coefficient of 18 W/(m^2 degree C), and by radiation to the surrounding surfaces at 10 degrees C. The total rate of heat loss from...

I have a circular cross-section of steel, around which I have air of constant temperature flowing. I want to calculate the heat flux, but I don't have the value of heat transfer coefficient,h (W/m^2.K) between steel and this air at 350C. Please suggest how to get the value for h. I am neglecting...

Homework Statement There is a Pressure-Volume diagram of an ideal gas. The processes make up a (rough) triangle. At constant pressure, we have point A to point C to the right of it to point D to the right of C. Then above A we have point B. C goes to B and D goes to B.. thus forming something...

Homework Statement Note: I know the wording of this post may be lengthy but the problem shouldn't take too long in theory and it's a basic problem from an introductory thermodynamics class so I desperately wish to understand this beginning part so I don't fall behind, so I'd REALLY appreciate...

Hi all I was just wondering about the dependence of radiative transfer from a body, on its surface area and not the volume. As per stefan's law, the variation is (StefanConstant * SurfaceArea* Temp^4) The primary source of these electromagnetic radiation is from the charges in the body...

Hello, I'm brushing up on my heat transfer / vector calculus, when I realized that my notes were all for isotropic heat transfer. i.e. q(vector) = k(scaler) del(u) However, there are cases, such as pyrolytic graphite where the thermal conductivity, k, cannot be described as a scaler...

Homework Statement Calculate the amount (in grams) of ice at 0 degree celsius that must be added to an insulated cup with 250g of water at 40 degree celsius to cool the water to 35 degree celsius. ignore heat transfer to the cup. given data: T(initial) water= 40 celsius T(initial) ice = 0...

My geometry is bit complex. I want to make a heat transfer model based on FDM in the radial direction. But it has become very difficult to discretize the domain because of multiple materials. As the segments are symmetric, I want to model the heat transfer in one segment. My schematic is given...

Hello, friends: I just got done studying a chapter in a physics text that explains how heat transfers from higher-temperature objects to lower-temperature objects. Unfortunately, that chapter said little about why heat transfers from higher-temperature objects to lower-temperature objects, so...

let's say heat change between system and surrounding, so the process must occur in infinitesimal steps ie, infinitesimal temperatures here. my problem is, how can we causes that to happen this way? i found some sources saying that, this is due to the large size of the surrounding. How are they...

I'd post this as a homework question, but I don't even have a real basis for it, and what I want is an equation. So my car sits out in the sun, and this causes the air inside the car to get hotter. My question is, what equation determines the inside temperature of a car out in the sun? I'd...

I have an assembly where I'm using a starwound cable heater to heat up a flow of air. But the air is not heated to the desired temperature. So I have decided to increase the heat transfer area by using metallic wool or some meshing around the heater. can anybody please suggest me which one would...

"multiplying equations" - spiral coil heat transfer Hi, I was wondering if anyone could explain to me what is meant in this article by "Multiplying equations 8 & 9". I have both equation 8 and equation 9 however I cannot seem to work out how to get equation 10...not sure if it's something...

I am getting crazy values so I need help. I want to find out how many watts or even Kw I need to heat up a space. Here are the givens: Sizes: Width:1.1176m, Length:1.6764m, Height:1.8288m Temp-outside: -9.44C Temp-inside:12.78C Material: Steel[thinckness(.00635m), thermal K=43] I just...

This might be a question with an obvious answer, but i want to make sure. During the phase changes from a gas to a liquid and from a liquid to a solid, the gas must give off heat, right... so the air around it gets warmer since the surroundings gain heat?

Hi Everyone i am new to this forum..the reason why i am here is a problem, i really want to discuss here. I am working on a thesis on optimization of a circular fin. But i want to know how can i start to solve the heat equation. the preferred method to solve the problem is Numerical...

I am currently working on a small personal project. It is a small under-water generator/ motor so the setup is as follows. The generator and gearbox are mounted on steel struts within an air-tight nacelle of sorts which is cylindrical and made of steel. The nacelle is submerged in cold water...

I am working on a project involving this setup (please refer to the pic). Basically compressed air at a constant flow rate flows through a 1/4" tube to the tube shown and gets heated by the star-wound heater and, this hot air heats the small inner vessel and then leaves the system. Now I am...

I’ve measured the temperature in my house over time - after turning off the air conditioner. I have a time series of internal temperatures for a fixed outdoor temperature. Is it possible to calculate heat transfer coefficients of my house using this data? Is it possible to relate these heat...

I am trying to set up for an experiment, and I need to know the time dependence of the temperature of the front surface of an assembly of plates. The assembly has a heater on one side and is exposed to a gaseous environment (of constant known pressure and temperature) on the other. I am...

Homework Statement Radiation is a type of heat transfer but I don't understand how it works. I know that conduction is direct contact and convection uses mass transfer to move heat but what does radiation do. My teacher never gave clear examples so some examples of how applies to heat transfer...

I don't seem to understand Clausius inequality at all. Really. It was deduced to me that the Clausius inequality is given by dS = \frac{\delta Q_i}{T} > 0 where Q_i is the irreversible heat transferred to a system. Though I cannot find a way to prove an assertion my teacher said: through...

When I read some heat transfer book, I got a problem. There are some numerical calculation methods in dynamic heat conducting in tube wall, but all the methods assume the temperature on one side of the tube and then calculate the temperature distributed in the wall. But are there some methods...

If I connect copper strip to the heat sink of my PC and then dip the other end of the strip in cold water. Will it help in cooling the heat sink and in return the PC. I shall be thankful for your answer.

Hi everybody, this question is on an old exam paper given to us for exam prep purposes. No answers have been supplied however. Am I on the right track? Question: A mass of 0.2kg of saturated refrigerant-134a is contained in a piston-cylinder device at 200kPa. Initially 75% of the mass is in...

Hi. How can i find out the temperature rise in a steel plate of known dimensions, when exposed to sunlight, losing heat to air flowing over it by convection, and heat getting transferred to another body by convection? I hope to hear about the different approaches that could be taken. Thanks...

Homework Statement hi there, I'm working on an annealing furnace. ingots are warmed up in the oven. I'm doing this with a finite elements method called Comsol Multiphysics. This is a pretty complex software program. Can someone please help me with this part of ComsolHomework Equations it is...

Hi All, I'd be grateful if helped in this understanding; I'm following the attached pages to solve a numerical problem by Forward difference, backward difference and central difference- in fact to be precise, deriving the transient solution approach to a heat transfer problem--- In the...

Homework Statement This questions relates to solar radiation and heat balance. I'm having trouble with part (b) of the question, having solved (a) already. The question is found in the following image: Homework Equations The Attempt at a Solution...

Heya, I'm a little confused about the heat equations and the difference in concepts and applications. So there's: Q = UA delta T <- I've used this for general heat transfer, like conduction through walls... Q = UA delta T(log mean temperature difference) <- I've used that for...

Homework Statement a sphere of radius 1/2meter, temperature 27*C, and emmisisvity 0.85 is located in an environment of 77*C. What is net flow of energy transferred in 1 second. Homework Equations So in my notes i have notes that say "heat transfer by radiation": P= stefans constant...

Hey guys, I am completely stumped right now (in many different ways). I am a senior in Electrical Engineering and just started an internship this summer. Sadly, they put me in a setting which involves nothing I have studied except the pure math (there is not a volt or ampere that I have...

Hallo, I have been trying to find some bibliography about this issue, but all what I found it is very simple and always discarding the effect of the Thermic Capacity of the elements. I have to work with matherials which operate in transient conditions and which have parts which accumulate...

Hi All I'm embarking on a model of a large physical system. I have a reasonable concept of the model but need advice on which simulators or programming languages to use. I've developed a (simple) explicit finite difference algorithm in excel for 'a few metres' and 'a few timesteps'. I have...

Hi all :) I'm trying to figure out how much heat I can save from covering a tank which is open (uncovered). The tank is rectangular made of steel and is filled with water, heated to 50C, and is not insulated with any material. The outside temp and humidity is assumed to be 25C and 60%...

So this concept is confusing me. You have a 20GPM, 150Degree F, 40PSIG water coming into a heat exchanger through a 1" diameter pipe. Chilled water is available for cooling from a 6" diameter line at 40 Degrees F, With a pressure of 110PSIG and a flow of 270GPM. The original...

Homework Statement A spherical black body with a radius r and a temperature T is placed in a spherical thin shell (radiation screen) with a radius R. The shell is also absolutely black on both sides. The space between the shell and the sphere and the space outer of the shell contain vacuum...

good afternoon i have a project to build a water dispenser. I'm strugling with heat transfer equations since it's cold that is being transfered. do i use the standard heat transfer equations even for cold? which equations do i use. water will be inside a 100x100x150 (1.5 litres) casing made...

Homework Statement I am currently writing a program that will calculate the heat transfer between a single pane window. All the qs I calculated were supposed to come out the same but q2 seems to be massive. Homework Equations Contained in the program. The Attempt at a Solution...

Preheating was carried out on a 4140, 2 inch dia. solid shaft material prior to welding of linkage plate and bearing was attached on the shaft. Temperature range is around 400 to 450 degree celsius. Welding was performed and followed by Post heating of temperature range 560 to 570 degree celsius...

Homework Statement The following problem can illustrate the economics of insulating the floor above the vented crawl space. A) If the composite structure of the floor is made up of carpet (R value of1/2 〖ft〗^2-h-F/Btu), subfloor (R=1), and air space between the joists (R=0.8)then find the...

Refer to the attached picture, condition : assume steady state legend : red : insulated (adiabatic) black : no condition Green : Temperature distribution, T(X) I started with figure A, from heat equation, A u will get the distribution with is just a constant...

question is 100.0 grams of copper metal initially at 100.0 degrees Celsius, is added to a calorimeter, containing? 250.0 grams of H20 at 15.0 degrees Celsius, if the specific heat of copper is .389 J/g Celsius, what is the final temp of the water and copper mixture? You can use this equation...

A room has a surface mean radiant temperature of 20oC. if a heat source of area 2 m2 at 200oC is introduced into the centre of the room, what is the rate of radiative heat transfer in kW? Can anyone help me with this question? I can't find any examples in my notes or online and need help quick...

Basically, I need to solve a transient heat transfer conduction problem. I've got most of the work done but I need to solve the problem using MATLAB or C++ or some other kind of coding. That's what I need help with. The actual aspects of the problem aren't really that important, so I will try...

Homework Statement A Brick is 8cm think and has a thermal conductivity of 1.10 J/(s.m.degreesC). Styrofoam insulation is 3cm thick and has a thermal conductivity of .010 J/(s.m.degreesC). The bricks are used to line a furnace a) if the temperature on one side of the brick wall is 500...

Homework Statement The application of the Heat Transfer Coefficient in the case where the surface area of heat flow is decreasing Homework Equations h = q/A * delta T h = cal/sec/M2 ( C ) q= cal/sec A= M2 delta T (C).The Attempt at a Solution If the surface area, A, is decreasing, then is...

Homework Statement We have 5 cm of external diametre tubing with 200*C of superficial temperature. The boundary temperature is 20*C and the convective heat transfer coefficient is 3.0 W/m^2*C What is the heat loss Homework Equations q = U*A*(T1-T2) 1/U = 1/h1 + [r1 * ln...