Heat transfer Definition and 875 Threads

Hi guys, could you concretely explain me (also with a simple example) the difference between blackbody emissive power (sometimes found as e'λb) and blackbody radiation intensity (i^{'}_{λb})? and which the difference between a diffuse surface and a surface that follows the Lambert law? Thank...

A cylindrical rod of stainless steel is insulated on its exterior surface except for the ends. The steady-state temperature distribution is T(x) = a-bx/L, where a = 305 K and b =10 K. The diameter and length of the rod are D = 20 mm and L =100 mm, respectively. Determine the heat flux along...

A heat transfer of 9.5 x 10^5 J is required to convert a block if ice at -15°C to water at 15°C. What is the mass of the block of ice? So do I have to use the equation; Q= mcΔT ? and Q= mL ? And if so how do I use it?

Hi all, We got these rad reflector foils to improve your heating bills in our shop today. Trying to figure out if there any good. As a really quick test to see if they do anything, i stuck one to the kettle and measured the temp difference with a thermal imaging camera. (pics attached)...

Hi everybody! I am working in a solid state physics group and need to find some heat transfer data to finish my calculations. I need to find the Nusselt number Nu=\frac{hL}{K} describing the heat transfer interface between a Si wafer and helium gas at a variety of temperatures. To find this I...

Convection heat transfer rate decided by Newton's cooling law doesn't have a relative velocity between the fluid and the solid surface term. But intuitively doesn't blowing faster on a hot surface make it cool quicker?

Could anyone please illustrate me about radiation by an illustration? If don't mind, animation could be great.

Homework Statement A cavity block wall of area 10m2 constructed of 100 mm concrete, 50 mm air gap, 50 mm of polystyrene and a second 100 mm wall of concrete. The wall contains three windows with dimensions of 0.5 m x 0.7 m with glass 4 mm thick. The outside temperature is 5 °c and the inside...

Homework Statement In an electrically heated home, the temperature of the ground in contact with a concrete basement wall is 13.8oC. The temperature at the inside surface of the wall is 20.8oC. The wall is 0.118m thick and has an area of 9.43m2. Assume one kilowatt*hour of electrical energy...

I'm curious how heat transfers between the heating element in my electric oven and the air in the oven. Say when I first turn on my oven the air is at room temperature (say 70F) and the surface temperature of the heating coil is at say 500F. After some time passes, the air in the oven rises...

Hi! Im doing some measures on a closed water tank with the water temperature 14C and surrounding air with temperature of 20C. I want to know how much heat transfer there is between the surrounding air and the tank. A= 47m2 (area of tank in contact with the surrounding air) Q=UA...

Homework Statement If you lie on the ground at night with no cover, you get cold rather quickly. Much of this is due to energy loss by radiation. At night in a dry climate, the temperature of the sky can drop to -40°C. If you are lying on the ground with thin clothing that provides little...

Homework Statement I performed an experiment using a double pipe heat exchanger. Readings were taken at steady state. Cold water entered the inner tube at 9°C, and its exit temp was 81°C. (flow rate was measured). The outer tube contained steam at 133°C and this temperature remained...

Homework Statement How many grams of steam at 100 deg. Celcius would be required to raise the temperature of 35.8 g solid benzene from 5.5 deg Celcius to 45.0 deg Celcius? Assume that heat is only transferred from the steam (not the liquid water) and that the steam/water and benzene are...

Hey, I am working on a thermodynamic design problem, and am trying to come up with some coefficients to modify Qin through a metal surface that is painted different colors. I know that there would be a significant difference in heat through the surface if it were black as opposed to a...

Imagine two cylinders in which one cylinder in within another.(Please refer attachment) The annular space between the two cylinders is filled with air. The outer cylinder is provided with a substantially large cut out The inner cylinder is maintained at a temperature say 200 deg c I...

Hello Wondering if anyone can help me towards finding an equation to calculate the heat transfer due to forced convection? Can't seem to find a good source for one at all, needs to be referenced for my MEng project. Currently have for natural convection: Q = h A (ΔT) Thank you...

Im trying to figure out how to calculate the pressure necessary to create a 30 degree celsius temperature drop in water, by using a small pressurized cylinder of air within the water. The volume of the water is .00075 m^3 and the volume of the canister is .00025 m^3. I calculated the amount of...

Hi there, I'm having a great deal of trouble with this thermodynamics question. Cylinder filled with steam at 350 kN/m2. Initial volume is 0.05 m3. Sufficient heat transfer is effected to raise the internal energy in each cylinder by 50 kJ. The piston is moved slowly to maintain the...

Homework Statement Given the two domains pictured below, calculate the heat transfer rate (Q [W]) for each case. http://img6.imagebanana.com/img/83fe4j54/Selection_001.png The domain on the left is insulated on the left, right, and right half of the bottom side, while the domain on the right...

If I had water at 180 degrees and dropped the temperature to 160 degrees over a heat exchanger, would I have the same BTU output as if I had water at 100 degrees and dropped the temp to 80 degrees? Delta T is 20 degrees for both situations. I know if we were talking about Ke related to mass and...

Hi, I'm interested in the theory of an Aluminum sphere that is initially at some temperature that is hotter than its surroundings. The sphere is surrounded by air at some small radius, say one meter, and then the air and sphere are both enclosed by an infinite shell of Aluminum at some...

In a heat transfer with internal heat generation what does the term "internal heat generation" mean? Is that applicable only if a body itself produces some heat (Like current carrying wires,nuclear fuel rods etc) Or if i have a two cylinders one within another,and if inner cylinder is heated...

So, I know that it has been sort of asked in other forms before, but they mostly deal with human beings and so I've yet to find an answer to the specific part of this quandary: if a mechanical system is exposed to space (with just the skin of the ship itself as the only boundary between heat...

Homework Statement I have a general concept inquiry. I was doing some thermal homework, and calculating values of Q in a given cycle. One process was isothermal, however it turned out that Q was not zero, causing me to wonder: How can there be a heat transfer in an isothermal process...

Hey all, not sure if this is where I'm supposed to post this question, but it is all about heat transfer. So this is part of my design project for my 4th year of chemical engineering. Problem Statement: A hollow cylinder 400 m long has hot combustion gases T = 500 Celsius flowing through...

Homework Statement A small pond has a layer of ice 1cm thick floating on its surface. The air temperature is -10 C. Steps (a-c) should help you fi nd the final answers in (d) and (e) (a) What is the temperature of the liquid water just below the ice? (b) Write the expression for...

An insulated Thermos contains 122 g of water at 91°C. You put in a 13.7 g ice cube at 0°C to form a system of ice + original water. Use mc(ΔT) |water + mc(ΔT) |ice + Lm |ice = 0 Final T = [(m*c*T) |water + (m*c*T) |ice - (L*m) |ice] / [m*c |water + m*c |ice] Final T =...

I have a quick question regarding the interrelationship between heat transfer and thermodynamics. Basically, since temperature as governed by the equations from the study of heat transfer, is neither uniformly distributed (a field) and changes with time (non-equilibrium), how applicable are...

I'm designing a vertical farm prototype and I'm trying to do some preliminary calculations to get an idea of how hot my crops are going to get. The basic design consists of a low-e glass (SHGC=.39) in the front and an aerogel panel in back(see attached diagram). I'm calculating for the hottest...

Homework Statement We are having a fictive, non existing heat exchanger with the following parameters: Outer tube diameters: 20 & 12 mm Wall thickness inner tube: 1mm, outer tube; 2 mm flow area hot side: 0.0226m2, cold side; 0.0272 m2 The heatexchanger is going to cool some hot...

Homework Statement ==================== <---- aluminium plate ⁣⁣⁣⁣⁣⁢⁢⁢⁠⁡⁡⁢⁢⁢...O .....O... <---- heat coil(O) Given an aluminium plate put on 2 heating coil(O), assuming no heat loss, how much is the heat transfer rate from the coil to the plate? Put the power of each coil as W...

Homework Statement A cube of Al (.1m x .1m x .1m with mass=.27kg) is placed on a large thermal mass maintained at constant 40 C (313 K).The cube is separated from the thermal mass by a .01m thick glass plate (.1m x .1m). If the Al block is initially at 10 C, how long does it take to reach a...

First off, I can't believe I never decided to search for a forum like this, I love smart people! lol. Anyways I am working on a Liquid cooling project for a highly overclocked computer system. Originally I wasn't going to use a heat exchanger(Matter of fact, until I stumbled across one on a...

Hey guys I really have difficulty learning heat transfer and I wish if someone knows a website that includes experiment or some kind of help. Thanks and I appreciate your time

Hi everyone I have a quick question regarding heat transfer. I have yet to study heat transfer yet but I have a basic understanding of the mechanisms from general physics courses. My particular question is regarding airflow across a surface and its ability to cool a heat source. The situation...

Hello everybody, I would like your comments on my findings and perhaps prompt me to look at relevant literature. Consider an enclosed airspace 1m length, 1m height, 0.5m width. At the center of its one 0.5 side a fan is drawing air out of the chamber through an aperture(steady, low air...

Homework Statement Determine the temperature of the filament of a 60watt lamp, if the filament has an area of 10mm^2 and an absorptivity of 0.35. Assume stefan-Boltzmann constant is 5.67*10^-8 W/(m.K^4). Homework Equations The Attempt at a Solution The equation I have attempted...

Homework Statement A silicon chip measuring 5mm by 6mm and of thickness 1mm is embedded in a ceramic substrate. At a steady state, the chip has an electrical power input of 0.3W. The top surface of the chip is exposed to a coolant whose temperature is 20°C. The heat transfer coefficient for...

does a cup of coffee, say 85 degrees C in a 20 degree C room, lose more heat due to radiation or conduction. In general, do common objects lose more heat due to radiation vs. conduction?

Why does the different in temperature between 2 body determine the rate of heat transfer? Why does the temperature gradient decrease as it reaches thermal equilibrium/fixed point of a substance? Apart from using the equation Rate of heat transfer = kA (Difference in temperature) / d How...

If we have a pipe with dimensions D=0.006m L=0.01m and a mass flow of m' = 0.019 kg/s How can we determine the heat transfer coefficient of the pipe?

Estimate how long a time it will take to cool a trailer filled with coke ? Given the ambient temperature is 22 degrees C and heat transfer provided by the refrigeration unit is 10 kW and the drinkable temperature is 4 degrees C. Make reasonable estimates of how much insulation is included on...

I have a quick question that maybe someone can help me out with. Let’s say I have an object that has a heat output of 48.7 KJ that is constant and it is surround by hydrogen that it flowing around it. Like a rock in a stream. If I know the starting temp of the hydrogen how would I determine how...

Homework Statement I don't really understand something in my textbook. It says the heat Resistor (how to say that in English? I hope it's alright like this...) trough a cylindrical tube (from the inside to the outside or revers) would be: R(heatrisistor)=1/2∏Lλ * ln (R1/R2) And then my...

Hi Guys, This is for my university project.I need to design a oil tank for the formula student car.The first stage is the analysis of the existing stock oil tank (Aprilia SXV 550 is the engine).I need to find out the heat lost/transferred from the of the existing oil tank.How can I calculate...

Hi Guys, This is for my university project.I need to design a oil tank for the formula student car.The first stage is the analysis of the existing stock oil tank (Aprilia SXV 550 is the engine).I need to find out the heat lost/transferred from the of the existing oil tank.How can I calculate...

I found the following: We have already seen that the flow of heat through conduction occurs when fast (hot) atoms collide with slow (cool) atoms, transferring some of their kinetic energy in the process. One might wonder why the fast atoms don't collide with the cool ones and subsequently speed...

Homework Statement A space station in outer space (far from the sun) has a total surface area of 580 m^2 with emissivity of .62. The temperature of the outside surface is 156 K. the walls are .25 m thick with an average thermal conductivity of .038 Wm^-1K^-1. Find the temperature of the inner...

Hello, My attic gets blazing hot in the summer days, i have installed more than enough electric fans, my house just never gets shaded and the attic is quite small. my first idea was to build a giant shade producing robot. after that, I decided to vent all of my A/C air into the attic...