Heat transfer Definition and 947 Threads

Hello Gentlemen, Long time reader first time poster. I have a problem that I am trying to solve below. Problem 1 A metal copper rod say 20mm diameter has a constant heat applied to it of 150°C on one end. Ambient temp of Air is 25°C. What length rod do I need so the other end is...

Hi all, I am trying to mathematically proof that one can neglect convection and radiation when two cubes (paraffin-based, 1x1x1cm) are in direct contact on one side whilst the other 5 sides are perfectly insulated. Any ideas on how to calculate the Nusselt number here? How do you justify that...

Heat Transfer Qts Engine oil at 60 oC flows over flat plate whose temperature is at 20 oC with a velocity of 2 m s-1. The length of the plate is 5m. What is the film temperature and the rate of heat transfer per unit width of the entire plate? Additional information (at the film temperature)...

Heat Transfer Qts Engine oil at 60 oC flows over flat plate whose temperature is at 20 oC with a velocity of 2 m s-1. The length of the plate is 5m. What is the film temperature and the rate of heat transfer per unit width of the entire plate? Additional information (at the film temperature)...

Heat Transfer Qts Engine oil at 60 oC flows over flat plate whose temperature is at 20 oC with a velocity of 2 m s-1. The length of the plate is 5m. What is the film temperature and the rate of heat transfer per unit width of the entire plate? Additional information (at the film temperature)...

Engine oil at 60 oC flows over flat plate whose temperature is at 20 oC with a velocity of 2 m s-1. The length of the plate is 5m. What is the film temperature and the rate of heat transfer per unit width of the entire plate? Additional information (at the film temperature): Thermal...

Homework Statement A power plant generates 1300MW and operates at 315 °C a 20°C heat sink is available. what is the minimum rate at which heat must be discarded? Homework Equations not really sure how to begin this one, have a feeling it is related to dq=Tds at constant pressure giving...

A perfect gas is compressed in a cylinder reversibly according to the law pV1.3 = C. The initial condition of the gas is 1.05 bar, 0.34 m3 and 17 oC. If the final pressure is 6.32 bar; and given that cv = 0.7175 kJkg-1 and R = 0.287 kJkg-1. Calculate the following. (a) The work...

Homework Statement A straight, rectangular fin made from 2024 aluminium has a thickness of t = 3mm and length L = 20mm. Base temperature is 100 °C and it is exposed to a fluid at 20 °C. h = 60 W/m^2-K k = 185 W/m-K (a) Determine the heat transfer rate from the fin to the fluid per unit...

let say i have a piece of metal cylinder (say 3cm dia) and heat it to 500 c, and put it inside a hollow cylinder with inside diameter 3cm (so they are touching) and outside diameter of say 8 cm), the hollow cylinder is empty inside so water pass through. is there anyway to calculate the heat...

Q2​A large wall of thickness 5cm and thermal conductivity k = 0.65W/mK has a front surface with an emissivity of 0.8. At this surface there is radiation exchange with the surroundings and convection heat transfer to the air. The air and surroundings are at 22˚C, and the convection heat transfer...

Noobie question... Where there is Heat there is movement, so does that mean that whenever heat is present matter cannot be solid?

There is a course at my school called nuclear power engineering. It's an optional course, but it sounds important for a nuc engineer. The course has two prerequisite courses: fluid mech, and heat transfer which i can take as electives. The thing is that I didn't take statics or dynamics (not...

Hi, I need help tackling this problem and I wanted help since I feel lost. I have a probe running through a belt-furnace that has multiple stages for heating, I know the temperature of the oven at any given time (in minutes), the oven takes 8 hours and the Temperature profile looks like this...

Homework Statement A counterflow, concentric tube heat exchanger is used to cool the lubricating oil for large industrial gas turbine engine. The flow rate of cooling water through the inner tube (Di = 25 mm) is 0.2 kg/s, while the flow rate of oil through the outer annulus (Do = 45 mm) is...

I have three temperatures (temperature of the fluid going in, temperature going out, and the temperature of the surface of the tube). What I'm trying to figure out is the film temperature at which I should evaluate the flow properties. The film temperature is defined as T,f = (T,s +...

Hello everyone, For the purpose of my study I would like to know the relation between Pressure and Convection Heat Transfer. Especially the rough pressure when the convection becomes less significant. I did not find satisfying results on the forum. I have to study the global heat transfer...

Homework Statement A styrofoam cooler is in the shape of a rectangular box. Its interior dimensions are 30×40×60 cm. Its walls are 1.5 cm thick. It contains 4.0 kg of ice with the remaining space filled with water. The ice and water are in thermal equilibrium. The outside temperature is...

Hi there, I am doing a project modelling and simulating a gas engine waste heat recovery system using an organic rankine cycle. As part of this project I would like to size the surface area of a heat exchanger (if only roughly). I have found the appropriate formula using Q = U.A.LMTD and...

Have a fluid flow in a cylindrical pipe with insulation around it. The insulation is in the shape of a truncated cone. It starts at a thickness with a radius only slightly thicker than the pipe and the radius increases as you move along the pipe. The radius increases at a constant rate. The...

Hello. I am about to show how heat is transferred through crystals i. e metals I know that it should be about conduction, and that the single quantum oscillators start vibrating in higher modes, due to the extra energy. Now is the question: HOW exactly is the energy trasnferred...

\Homework Statement Air is compressed in a piston-cylinder assembly from p1 = 10 lbf/in2, T1 = 500°R to a final volume of V2 = 1ft3 in a process described by pv1.25 = constant. The mass of air is 0.5 lb. Assuming ideal gas behavior and neglecting kinetic and potential energy effects, determine...

Hey guys, first post. I'm trying to determine to the rate at which liquids drop out of a gas pipeline. I've modeled the system in a chemical process program, but its only a steady state model. Anyways, here's some of what I can get out of that program: Heat of vaporization Total Heat Transfer...

Homework Statement A piston-cylinder assembly contains air, initially at 2 bar, 300 K, and a volume of 2m3. The air undergoes a process to a state where it pressure is 1 bar, during which the pressure-volume relationship is pv = constant. Assuming idea gas behavior for the air, determine the...

When does the Classical Heat transfer fail / stop to work , i.e, when will the quantum effects have any effect on the heat transfer. My problem is a heat transfer between a Spherical Bacterial Spores(an agglomerate) and a hot gas (take Nitrogen) . I really don't know whether the spores can be...

Hi there, Had a physics project in university that looked at the heat transfer of a pipe in a cement block for snow melting. When I modeled it using computational fluid dynamics, I just did a 2D model and simplified it by saying that the fluid would be moving fast enough through the pipe that...

I attached the problem of interest (probably the only part you guys need to see is the equations at the bottom). My answers are off by a magnitude of 10 compared to the solutions. (copy and pasted it below since the pic is a little hard to see at the bottom) q = σε f*A(T^4 − Ts^4 ) = 5.67...

We have a pan that is used to boil water. There are 2 surfaces to the pan. One is touching the water and the other is touching the stove, obviously. We have heat that is transferred to to pan's bottom. I know what all 3 are and process of elimination tells me this is conduction. Is it...

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...

Hello, this is my first post, so please forgive me if I am not doing this exactly right. I am working on a problem in which I have an open top cylindrical tank that contains a fluid at a higher temperature than the ambient air temperature surrounding the tank. What I am trying to determine...

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...

Homework Statement A thermometer for medical applications to determine the time required for the tip to reach a temperature of 37.95 C when in contact with the skin temperature of 38 C, starting from an initial value of 25 ° C. Admit that the tip of the thermometer is completely metallic...

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...