Heat transfer Definition and 875 Threads

Hi guys, Hoping to see if I can get a bit of help with a heat transfer equation. Apologies if this is not in the correct forum as this is my first post. I need to find out how long it will take a bag of 1000L of water (in a 1m3 cubic bag) to heat up to a specific temperature. The bag is...

First off I would like to say that this is not a homework question. I am trying to calculate the temperature of a very thin piece of steel. Assumptions The underside of the metal is perfectly insulated To = 20C (initial temperature of material) Q"=3000W/m^2 (heat flux) K = 51.9W/m*K...

My first posting, so apologies if this is in any way inappropriate to the forum/section. I am asking here for some scientific input to this question about a cooling system as, for example found in a classical motor vehicle; what is the likely relationship between coolant flow and heat...

As I remember learning in school, heat cannot flow from cold to hot. But isn't that true only for conduction and convection? Radiation heat is purely Infrared waves, and there should not be any issue with that. Please correct if I am wrong.

Hi, I want to know the peak temperature attained and temperature distribution with time in a frictional welding process ( ultrasonic consolidation between an Al substrate and Al strip). The problem with normal thermocouples is that by the time it shows the temperature , the temperature has...

this question was posed by someone on a computer forum and is probably easy for some of you, so here goes : imagine water in an open container which is perfectly insulated on the sides and bottom. the water is stationary and heat is being added from the top (assume that the surroundings above...

I noticed that my tea heats up faster than the cup it's in when I microwave it... how come? aren't solids more conductive? Also... I was wondering how the notion of vibrating atoms/electrons (heat) squares with quantum mechanics, probability waves and such?

From what I gathered in Heat transfer, an object in space, ie space shuttle, can only lose cabin heat through the means of radiation (no conduction or convection off the surface...) So how would one go about determining what the emissivity is in space. Obviously there will be objects that are...

When room temperature is at 19 degree centigrade, I found that water temperature is at about 20 degree centigrade a small plastic cup at volume of 3ml, filled with 1ml of water, put in a secluded shaker at the temperature of 42 degree centigrade, , what should the water temperature...

I'm working on a project that involves putting electronics equipment into a solid metal (aluminum) case. The cases are sealed watertight and I need to be able to transfer the heat originated at the electrical components to the ambient air. I can perform the analysis to get a pretty good idea...

I'm in need of an equation that relates the loss of heat (in power) of a cable to ambient air to various parameters such as diameter, temperatures of air and cable, and all other variable that may play a role. My research online has produced some results, but I haven't quite found what I'm...

Homework Statement We have a wall of 30cm thickness, an inner surface temp of 500Kelvins and outer surfce temperature of 60Kelvins. Homework Equations thermal conductivity = k(a) = 60 + 0.0006a^2, where a = temperature. fouriers law = q = -kA(da/dx) The Attempt at a Solution...

Hi, I have nothing to do this summer so I figured I would like to model the heat transfer for different shapes and fluids and compare with experimental values.. :) Anyway I searched on google and found nothing. What are the main problems? For example is it acceptable to assume that the...

THe question is : Given the reaction CH3OH goes to CO + 2H2 Change in heat=90.7 a)endothermic or exothermic? b)Calculate amount of heat transferred when 45 g. of CH3OH id decomposed by this reaction at constant pressure. c)For a given sample of CH3OH the enthalpy...

The problem is about a cylinder with 3 mm thickness in the walls, roof, and ceiling. The walls, roof, and ceiling also have a k value of .0042 w/mk. Inside the cylinder is 64 degrees Celsius and outside its 22 degrees Celsius. The air outside the cylinder has a heat transfer coefficient of .3...

Im doing a project to put a heater in a car to pre heat it. I need to determine how many watts would be needed to defrost a window in a certain amount of time. I know the temp of the outside air and temperature to melt the ice is at least 0 C. I thought i could use it as a semi- infinite...

Homework Statement Find the amount of thermal energy that flows per day through a solid oak wall 10.0 cm thick, 3.00 m long, and 2.44 m high, if the temp of the inside wall is 21.1 C while the temp of the outside wall is -6.67 C. Homework Equations Q= k(A)(T2-T1)t/d coefficient of...

Hi all I've been calculating heat convection off a horizontal heated plate to still cool air around it. Since the plate has a size of 50m2 the GrPr number is turbulent i there's no equation in my book to calculate heat transfer by convection for GrPr > 10^11, so i used the equation of GrPr at...

I don't know if classical physics is the best place to put this, cause normally i would have put it in the engineering section. There is no governing equation right now to describe heat flow between 2 liquids? another question: flow between 2 liquids is governed by convection, if we place an...

Hey. I've been pondering on and off for a while now how exactly energy is transferred between two gas atoms, with different energies, via collision. Specifically how the electrons, photons, neutrons, protons, and any other particles that are used for energy transfer in convection, interact...

This is not homework, so I think this is the right forum. I am trying to write a program that simulates the heat transfer between, say two cubes of different volumes, heat capacities and thermal resistances. I know Newton's law of cooling just works dandy for say an object cooling in a fixed...

Homework Statement Rigid tank volume .5m^3 initially evacuated. Tiny hole develops, air seeps in @ 1 bar and 21 degrees C. Pressure in tank reaches 1 bar, slow leak so temp remains 21 deg C inside tank. What's amount of heat transfer? Homework Equations Q=T[S(2)-S(1)] Pv=nRT The...

In an electrical circuit, when current flows through a resistance, heat is produced. Is there some quantity (?) into which heat is transformed when it flows through a substance (all substances having some resistance to heat flow)?

ok, this is more of a question of theory than actual calculation. Me and my friends did a physics lab on heat transfer vs. surface area of contact. We used water and oil (since oil will float above the water and creating a surface of contact). We heated the water to ~50 degrees C and oil was...

im reviewing for my final in a few days an although this is a basic question i can't work out the correct answer for some reason. and i know i started the other thread below this one but i figured this was a different topic so the heading should be different lol Homework Statement A heat...

convection right?

A 20-20-5 cm slab of copper at a uniform temp of 200c suddenly has its surface temp lowered to 35c. Using the concepts of thermal resistance and capacitance and the lumped-capacity analysis, find the time at which the center temp becomes 90c. density =8900 kg/m^3 specific heat = .38 kJ/kg-k...

Hi can anyone temme how to calculate view factor between two spheres.

My book is fairly explicit when it comes to solving problems with rods of uniform temp, and fins that have a heat source at one end but I have a couple of HW problems that deal with rods. 1) A rod connected to 1 hot wall given: Wall temp environment temp dia. and length of rod heat...

An insulation system is to be selected for a furnace wall at 1000 deg C using first a layer of mineral wool blocks (k=.091 W/m-c) followed by fiberglass boards (k=.0425 W/m-c). The outside of the insulation is exposed to an environment with h= 15 W/m^2-c and temp of 40 deg C. Claculate the...

I've been working on the following problem for several hours but am not sure how to approach part (c). Consider the insulated vessel shown here, with compartment A of volume 0.03 m3, which is empty, and separated by an insulating membrane from compartment B of volume 0.01 m3, which contains...

[FONT="Courier New"]A 2 kg copper block, initially at 100°C, is brought in contact with a 2 kg plastic block, initially at 20°C. They are kept in contact long enough to reach the same equilibrium temperature. The specific heat of plastic is four times as much as the specific heat of copper...

Hi all! Could anyone tell me, a final year student in mechanical engineering preparing for his final year project, what the hot reserach topics in heat transfer are?

I am doing a photovoltaic experiment and I wanted to know if anyone knew the heat transfer value of a photovoltaic panel or how to calculate it.

I was wondering if anyone knew the heat transfer coefficient of a thin steel sheet on top of water. It is vital that I find this answer because it is a major part of my research. I found one formula which stated that the U value could be found by using the formula 1/U= x1/k1 + x2/k2. I wanted to...

An open container holds 0.550 kg of ice at -15 Celsius. The mass of the container can be ignored. Heat is supplied to the container at the constant rate of 800 J/min for 500 min. A) After how many minutes does the ice start to melt. This part I calculated and got correct, it's 21.7 min...

Does anyone know where I can find the governing equations on the heat transfer of a horizontal, closed loop system? e.g. http://www.eere.energy.gov/consumer/images/closed_loop_system_horiz.gif I've tried searching online, and all I can find is the general overview, no equations :frown...

Heat Transfer! Consider the following reaction: CH3OH(g) -> CO(g) + 2H2(g) Change in H= +90.7 kJ (a) Calculate the amount of heat transferred when 45.0 g of CH3OH(g) are decomposed by this reaction at constant pressure. (in kJ) (b) If the enthalpy change is 14.0 kJ, how many grams of...

Hey I am stuck on yet another one. This one has me stumpted becasue it has to do with a caliometry can and I am given mass of the can and water in it but i don't know if i should add them or have them in separate m*c*T expressions. Anywho here's the problemo: A laboratory technician drops a...

Hi all! I am currently choosing the topic for my dissertation, and am struggling between heat transfer and fluid dynamics. What would you guys say on these two discisplines? It seems to be that they are quite inter-related, and both of them are quite theoretical and mathematically intensed...

Question: How long does it take a 1000W electric kettle to bring 1.0L of water to the boiling point if the initial temperature of the water is 15ºC and the kettle is made of 400g of iron? Assume that no water is boiled, that no heat is lost to the surroundings, and that the kettle is 100%...

I would like to do a first principles heat transfer calculation for an ideal, monoatomic gas at entry temperature T, and pressure P flowing at velocity v (v is small, so flow is laminar) through a stainless steel tube at some uniform temperature T' > T. But if someone has done this calculation...

Hello all, I just need some clarifications on my approach to this question. Heat is absorbed along a metal bar from a hot thermal reservoir Th to a cold thermal reservoir at temperature Tc. Apart from the ends, which are in contact with the thermal reservoirs, the bar is perfectly insulated...

My question is as follows: If you wsh to save fuel on a cold day. and you're going to leave your house for a half hour or so, should you turn the thermostat down a few degrees, down all the way, or leave it at room temperature. I said that I would leave it at the same temperature since I'm...

id appreciate some input u guys... Heat Transfer and Calorimetry A 50 g Aluminum calorimeter contains 95 g of a mixture of water and ice at 0 degree Celsius. When 100 g of Aluminum, which has been heated in a steam jacket to 100 degree Celsius, is dropped into the mixture, the temperature...

I know the heat transfer diferential equation, but I only saw it being used when the temperatures of the extremities of the material are fixed. Is there any phormula that aplies for situations where at least one of the extremities is free to change its temperature? Ex.: the left side of an...

I have done a series of thermodynamics questions covering heat transfer, internal energy, temperature pressure etc. I have a new one but I am unsure how to start it, its unlclear whether i know certain things. I can do the question form looking back at pervious questions, if i knew how to start...

Hello, I have a test coming up and this is a question that will be on it... The wall of a house is composed of solid concrete with outside brick veneer and is faced on the inside with fiberboard. The fiberboard width is 2 cm, the concrete width is 15 cm, and the brick width is 7 cm. If the...

How could I calculate how much time would be required to melt a plastic through a composite material? Composite is .005 inches paper and .0003 inches of Aluminum Plastic is .001 inches polyethlene with melting point of 325 F Assume heat source is uniform across area of composite

During one hot summer, a physics grad student went to the local toy store and purchased a plastic child's swimming pool. Upon returning home, he filled it with 200 liters of water at 25 C. Realizing that the water would probably not be cool enough, he threw ice cubes from his refrigerator, each...