Heat transfer Definition and 947 Threads

Homework Statement One liter of water at 30 C (30000 calories ) A 100 gram sphere of ice at 0 C in center of water volume . The ice will absorb 80000 calories melting, and final water temperature = 22000 cal/1100g = 20 C. Assume mixing and uniform water temp during melting and water vessel...

Homework Statement A bare slab fuel element is 0.2 in thick. It has a kf = 10 Btu/(hr*ft*F) and a q''' = 5e7 Btu/(hr*ft^3). At x=0 (left hand face), h_lhs = 400 Btu/(hr*ft^2*F) with a fluid temp of 700F. At x=0.2 in (right hand face) the heat transfer coefficient is h_rhs = 300 Btu/(hr*ft*F)...

Homework Statement One liter of water at 30 C ( 30000 calories ) 100 gram (100 cc ) sphere of ice at 0 C is in center of water volume. The ice will absorb 8000 cal melting and final water temp = 22000 cal/ 1100 g = 20 C Assuming mixing and uniform water temp during melting ,and vessel is...

Hi. I'm trying to make a simple model of a condensation based countercurrent heat exchanger where liquid water and steam flows are separated by a conducting wall. I formed the equations as Q = \frac{T_{steam}-T_{water}}{\frac{1}{Ah_{water}}\frac{d}{Ak_{wall}}\frac{1}{Ah_{steam}}} = L\dot{m}...

Homework Statement Reasonably simple (I hope!) heat transfer problem: Smooth cylinder of diameter (D) 0.8m and length (L) 1.2m has a surface temperature (Tsurf) of 240C (513K). Ambient air temp (Tamb) is 30C (303K). Emissivity of cylinder (E) is 0.85. Heat transfer coefficient of convection...

Hi, Im working on a model where I need to look into the rate of heat transfer from a gas that's being compressed by a "liquid piston" of water. So basically a closed container containing a fixed amount of air n of volume V, is filled with water from the bottom until the volume of the air...

I need to use the equation ( thermal resistance for convection) R= 1/hA but I am not given an Area, I am only given 4 meters as a thickness. how do I find A to use for the equation to solve for R. Homework Equations The Attempt at a Solution

I need to use the equation below ( thermal resistance for convection) R= 1/hAbut I am not given an Area, I am only given 4 meters as a thickness. how do I find A to use for the equation to solve for R.

Homework Statement The following cylinder has a temperature inside Ti and temperature outside To. Using the general equation for heat conduction in a cylinder, write the temperature distribution equation as a function of the radius T(r). What is the temperature midway at r=a? (Take the heat...

Homework Statement The heat transfer into and from a gas, in one change in the condition of state is described with following formula: see attachments. Homework Equations Calculate the value of the heat content Q, when the values are V1=0,1 and V2=0,3. Give the answer in whole...

Hello, I'm having trouble getting started on this problem. Here's the question: [PLAIN]http://img810.imageshack.us/img810/2464/ee323assn3q3.jpg My issue is in setting up the governing partial differential equation in 3 dimensions. What I've tried so far is setting du/dt equal to the...

Homework Statement Two-tenghts Kmol of Nitrogen in a piston cylinder assembly undergoes two processes in a series as follows... Process 1-2: Constant pressure at 5 bar from V1=1.33m^3 to V2 = 1m^2 Process 2-3: Constant volume to P3=4bar Assuming ideal gas behavior and neglecting kinetic...

Hi, I have an easy problem for you I think but I'm not a specialist in thermo problems. Here is my problem. Homework Statement 2 plates in aluminum, one at T1=230°C and the other one at T2=30°C. In between, some air or something else (I don’t know yet). Homework Equations Equation...

I have an enclosure in which the electrical components put off 10,500BTU/hr. At the top of the enclosure the internal hot air is in contact with circular aluminum tubes. Ambient outside air at 70 degrees F is blown through the center of the tubes at 500cfm. Internal hot air and outside ambient...

1. Problem statement I've already posted this question in the advanced calculus help but it was suggested that I ask this in the physics forum. I can upload the pdf of my work again so I'll link to it https://www.physicsforums.com/attachment.php?attachmentid=31702&d=1296270924" from my other...

any good HEAT TRANSFER books out there?? Hi, I am looking for a heat transfer book for Graduate level. i am actually familiar with good undergraduate books like fundamental of heat transfer. please tell me a little bit about whatever book you are recommending thanks in advance

1.Two homogeneous rods have the same cross section, specific heat c, and density \rho but different heat conductivities \kappa1 and \kappa2. Let kj=\kappaj/(c\rho) be their diffusion constants. They are welded together so that the temperature u and the heat flux \kappaux at the weld are...

1. The problem statement: (a)Concider a stainless steel hollow pipe containing a saturated steam and has length L, cooled by convection & radiation. Find formula for T2. (b) Another question "Not related to the previous one": How would I know if a gas has gone turbulent? Homework...

1. The problem statement: (a)Concider a stainless steel hollow pipe containing a saturated steam and has length L, cooled by convection & radiation. Find formula for T2. (b) Another question "Not related to the previous one": How would I know if a gas has gone turbulent? 2. Homework...

Homework Statement A 0.25 kg piece of ice is warmed by an electric heater. Assume that there has been no loss of energy to the surroundings. It takes 150 seconds to heat the ice from -30° to -10°. How much additional time after 150 seconds will be required to melt all of the ice, assuming that...

Hi I am curious to know if anyone can provide a formula/answer to the affect of a thin layer of ice may have on heat loss in water flowing in a pipe. Example. I have a smooth plastic pipe approx 20mm diameter, 5m length. 400ml of water travels down the pipe, approximately 0.5m/s. in -10C...

I would be grateful for your help with a small project I am involved in at work. I would like to set up an excel spread sheet to calculate either the thickness of insulation required to reduce the temperature of say a furnace wall from the inside to the outside, or calculate the resultant...

Problem: Two surfaces exist, a hot and cold. Between them a span of air of a known distance and convection coefficient exists. If the temperature of one surface is known, what is a good model to predict the temperature of the other? Heat flux between the two is unknown. I kindly request...

confusing heat transfer... hi im really confused about the exact heat transfer mechanism of the phenomenon i observed the situations simple: if you immerse a red hot wire into water with small particles floating on the surface, the particles move really fast. at first, i thought it could...

Homework Statement Find mi, the initial mass of ice. Ti = -20 ci = 2093Jkg-1K-1 Ts = +35 ms = 2kg cs = 837.4Jkg-1K-1 cw = 4187Jkg-1K-1 lf = 3.35x105Jkg-1 S = solid W = water I = ice lf = latent heat of fusion of ice / waterHomework Equations Q=mc\DeltaT Q=C\DeltaT Q=mlThe Attempt at a...

I am planning a solar collector system for domestic hot water and heating. I am attempting to calculate the heat loss in a storage tank. If we assume: Tank Volume = 1m^3 Tank Surface Area = 6m^2 Tank Contents = 1000L water Initial Water Temp = 90C (194F) The Temp Outside the Tank = 10C...

I am currently working on a project that cools water moving through a chilled aluminum block. I am not familiar with the math/physics involved and would like some direction or recommendations. My project is currently setup so that I suction 32oz of 70 degree F water out of tank1 and pump it...

Homework Statement Homework Equations Newton's law of cooling Fourier's law The Attempt at a Solution Besides writing down both the laws and perhaps drawing a diagram, I don't really know how to go about this derivation. Any help would be really appreciated

if you plunge a hot metal (like wire) into water, the water temperature obviously increases. I wonder what kind of heat transfer occurs between the metal and the water. it clearly doesn't seem like convection or radiation. But I am not so sure if conduction is the right one cos it is usually...

Homework Statement I must solve this problem, please help me, which equations i should use? Most of us have passed our finger through a 800C candle flame and know that if we limit exposure to about 0.25 s, we will not be burned. Why not? Show all the calculations that support your answer...

Homework Statement Consider a double-paned window consisting of two panes of glass, each with a thickness of 0.500 cm and an area of 0.745 m2, separated by a layer of air with a thickness of 1.95 cm. The temperature on one side of the window is 0.00°C; the temperature on the other side is...

I am struggling a bit with this problem: I have a pipe with a constant surface temperature of 1100F. I also have a tank which cannot reach a temperature higher than 258F. I am trying to figure out the minimum distance between the two (in 80F air, which will be moving at a minimum of 5 ft/sec)...

Homework Statement The human body must maintain its core temperature inside a rather narrow range around 37°C. Metabolic processes, notably muscular exertion, convert chemical energy into internal energy deep in the interior. From the interior, energy must flow out to the skin or lungs to be...

Homework Statement Find the heat flow and the interface temperatures of the given figure. Homework Equations The Attempt at a Solution Do solve it correctly? I do not know how to solve the interface temperatures in case of parallel. Can you explain to me how to solve it

1. A cube 1m on a side is located within a cube of 2m on a side. If the cubes do not touch, what is the view factor between the outer surface of the smaller cube and the inner surface of the larger cube? 2. View Factor = the proportion of all the radiation which leaves a surface "A" and...

Need help to find the heat transfer coefficient for a stirred bioreactor any help on how do I go about...

Homework Statement An animal has a core body temperature of 37oC and a skin temperature of 34oC while in surrounding of an air temperature of 25oC. If the skin temperature fell, what would happen to: (i) the rate of heat transfer via conduction through body tissue? (ii) the rate of heat loss...

Homework Statement Hey all! So I have an exam coming up soon for my heat transfer module at uni and I'm fairly confident with the material, but in one of the tutorial sheets I have there are some questions which I don't know how to solve. I'm not really asking for a solution to these...

Hi, I am in a Heat Transfer class at school and my professor has set an interesting challenge before me. It is not a homework problem or anything, just a side project he challenged us to look into relating to external flow. The question is as follows: In fluid (e.g air, water) flow over a...

how to prevent a metalic ball not to being hot from the radius of the sun.

Homework Statement The 700m^2 ceiling of a building has a thermal resistance of 0.2 m^2K/W. Find the rate at which heat is lost through this ceiling when the ambient temperature is -10C and the interior is 20C. Homework Equations Newton's law of cooling: Q=hA(Ts - Tinfinity) The...

Homework Statement Milk is pasteurised by heating it to 72C for 15 seconds. The hot pasteurised milk is cooled by using it to preheat incoming cool milk. Milk enters a pasteurising system at 2C and a flow rate of 3000 litres per hour The incoming milk enters a preheating plate heat exchanger...

Homework Statement A thin sheet of ice with an area of 0.15m^2 on each side hangs from a roof. The ice is at 0C (Celsius) and the surrounding air is at 10C. The net rate at which radiant energy is transferred to the ice from the sunlight and from the surroundings is 20W; q=9.5W*m^-2*K^-1...

Is there a relation that connects a current with the diameter of a material for efficient transfer of thermal energy. I say diameter as I think its safe to assume heat leaves radially given a uniform material. I am also looking for a relation between resistance of a material and heat...

how would you find the gap size between 2 infinite plates given that the fluid is water and the plates are silicon? the temp of water is 20 C and I am assuming that the heat transfer coefficient is 390 W/m^2K. i remember doing this stuff in heat transfer with temperature profiles and stuff but...

Homework Statement How much water remains unfrozen after 50.2kJ is transferred as heat from 260g of liquid water initially at its freezing point? Homework Equations The Attempt at a Solution

hi, We had to do a prac. last week to investigate the effect of insulator materials on the heating of buildings. we did the prac, but unfortunately we didn't save our graph which shows the change in temperature with respect to time, for each of the different insulator. we had a...

Hello, everyone, I have a question on how to calculate the heat transfer and change in temperature for a project I am working on. It consists simply of a cooling water block (that you would find on a tec cooler etc), a fresnel lens, and a pump. The fresnel lens focuses the light onto...

Someone a while back posted a link to a thermally conductive/heat transfer pad. Can't remember the details, but I remember I was intrigued by it...anyone remember what it was? [yes, I know this is vague]

I need some help estimating the heat transfer of a system. If I have an exposed length of pipe with a dynamic fluid moving at a constant volumetric rate through a very hot room, what equation is most appropriate to calculate the exit temperature of the fluid? Given: Initial temperature of...