Heat transfer Definition and 875 Threads

A problem from a heat transfer book with conduction and radiation led me to a differential equation like this: T'(t) = a - b*T(t) - c*T(t)^4 Although my professor said that there wouldn't be an analytical solution for this one and to get the answer by an iterative method I got curious and...

Hi, I would like to know if somebody has the formulas to find the heat transfer coefficient while the nucleate boiling and the film boiling, for a plate heat exchanger... I really look forward reading someone. Thanks

A glass window 1m x 2m and .005m thick has thermal conductivity of 1.4W/m K. Inner surface temp of 15C and outside of -20C, what is the heat loss through the glass. double paned construction two panes separated by .01m, if glass surfaces are 10C and -15C, with air thermal conductivity of...

The graph is in the attachment! ( don't have to download to view the file)Homework Statement 49a) A 0.25 kg piece of ice is warmed by an electric heater and the following graph of temperature is produced. Assume that there has been no loss of energy to surroundings. How much additional time...

What is the *main* mechanism of heat transfer between a thermal resistance and water? My doubt arose in the context of a problem (from a high school national test) dealing with the following situation: a 500 W thermal resistance made of copper is immersed in a jar containing 500 g of water at...

Homework Statement determine the thermal effieincy of a heat transfer process where the following data has been used Input=3kW 1.7 litres of water have been heated from 313K to 375K in 2.5 minutes specific heat capacity of water= 4.19kj/kgK Homework Equations Thermal efficiency=...

Hi everyone! First time here, but I'm having trouble with a problem. Here goes: On a given day, heat losses through the 20cm-thick walls of a warehouse are 0.02 kW/m2 when the outside wall temperature is 5C and the inside wall temperature is 25C. The owner would like to reduce her heating...

Homework Statement where λ= thermal conductivity \dot{q}= dissipation rate per volume Homework Equations qx=-kA\frac{dT}{dx} The Attempt at a Solution I don't know where to start from to be honest, so any help would be greatly appreciated

Hello, I have 2 problems that are currently bothering me, and I would enjoy help with either. The more immediate of these problems is with my family's gas stove. Whenever we need water to boil, we put the pot on and turn the burner all the way up. My father then comes in and turns it...

I AM DOING A PROBLEM ABOUT TRANSIENT HEAT TRANSFER AND IT SAYS: "A solid sphere of steel has 1 cm of diameter and a initial temperature of T0 =15 ºC. It is placed into a flow of Tinf = 60 ºC where the convection heat coefficient is h = 2000 W/(m^2K): (Density of steel rho = 7832 Kg/m^3 ...

Dear all I got a value of 37 for h ( convection heat transfer ) Does it consider as free or natural convection heat transfer coefficient? Thanks in advance ! And Sorry its not a Homework problem :)

I am confused as to how heat transfer really works. I've read all about conduction/convection/radiation. Radiation makes sense to me, electrons enter a higher band, come back down and give off energy in the form of EM waves. These waves can then be absorbed by other atoms causing electrons to...

Hi guys, I have a question regarding heat transfer. When I have a piece of heated metal which is left to cool down in air, it goes something like this right? Heat is transferred to air by conduction (metal to air) then from air heat is given off by convection currents. Also, radiation occurs...

Homework Statement I am required to conduct a thermal shock test where by a stainless steel object (complicated geometry) is to go from one tank of light oil at -55°C to another tank of the same light oil at +140°C, then back the -55°C tank. This is to be repeated 5000 times. In order to...

I am looking to utilize flexible stainless steel corrugated tubing similar to this: http://www.pipesystems.com/site/index.cfm?id_art=24995&vsprache=EN as a heat exchanger immersed in a tank but have been having a tough time locating technical data on it other than the "surface area" and of...

Using heat transfer equation to find out heat transfer rate but reached a puzzling result, where did I do wrong? Problem statement: Heat transfer rate of a heated plastic plate in air, considering only one side, the size of the plate is 15cm X 15cm, assuming temperature difference is 1K...

Hi folks, Just a few general questions I have here. 1) The situation: A cubic block is taken from an oven and suspended so that both its top and bottom surfaces are exposed to the room air. Would the rate of heat transfer from the top surface be greater, equal to, or less than the rate of...

Suppose I have an object with a surface area of 2 square meters at a temperature which causes it to radiate energy at a rate of 1 kw per square meter. It has a very large thermal mass and so for the purposes of this experiment, a constant temperature . Around this object I have a system of...

Homework Statement Hi all, I have this problem statement with variables: 20" Diameter, 2000mm (length, L) cylindrical container with 8mm thickness made of plastic Container 3/4 filled with gasoline. Question: What is the immediately surrounding temperature required outside the container to...

A straight, uniform circular pipe of internal diameter of 88.43 mm and external diameter of 118.38 mm carries hot water at 63.67 deg cel. The pipe has a thermal conductivity of 247 Wm^-1 K^-1. how to calculate the steady-state rate of heat transfer per unit length, in W m^-1, when the outside...

i prepared a setup wherein i heat a nichrome wire with 3 volts battery, measure its power, the temperature of the nichrome and the temperature of air.. by using the formula ΔT=PRsurf where ΔT=Tnichrome - Tair P=VI Rsurf=1/hA, R is, basically, the thermal resistance to heat...

I'm trying to calculate the heat loss of efficiency due to increasing the mixture of propylene glycol in a heat transfer fluid compared to water.. For this I'm saying that water has a heat transfer efficiency of 100% (relative only) Im looking for multiple data points to create an equation...

Hi, I have a device which is heated from inside by constant heat (let's say by Joule's heat - UIt). Some heat causes temperature rise of the device, some is lost into surroundings through device's surface. I measured how temperature of the device varies with time and I want to calculate...

Homework Statement The temperature at the bottom of a pond of depth L IS 4°C. The temperature of the air , just above the layer of ice frozen at the pond surface is -2°C. THE THERMAL CONDUCTIVITY OF ICE IS THREE TIMES THAT OF WATER The thickness(X) of the frozen layer of ice must be-...

The temperature at the bottom of a pond of depth L IS 4°C. The temperature of the air , just above the layer of ice frozen at the pond surface is -2°C. THE THERMAL CONDUCTIVITY OF ICE IS THREE TIMES THAT OF WATER The thickness of the frozen layer of ice must be-

Hey, how would I start solving the total radiation transmitted through one plate, an air gap then another plate (double glazing) as well as the total convective heat transfer across the two plates? Thanks!

Homework Statement A solid body X of heat capacity C is kept in an atmosphere whose temperature is 300K. At t=0 temperature of X is 400K. It cools according to Newton's Law of cooling. At time t1 its temperature is found to be 350 K . At this time,the body X is connected to a large box Y...

I'm a game developer and I have an idea to make something heat up and cool off and I would like to use realistic style formulas to do the math. Instead of making it add dramatically over time. I basically need a formula for adding and removing heat from a 2 dimensional vector based on...

Hi all, I have a unique problem that I need some direction on. I have a .5x.5x.75 meter adiabatic chamber. No heat loss from chamber walls to the atmosphere. Inside the chamber there is an electrical flat heater plate .5x.05 meter with constant 100W. A fan blows air over the heater bar at...

Knowing the heat transfer rate q, how long does it take to lower a fluid from temperature T0 to Tf? This is for convective heat transfer from a heated body submerged in a fluid. I'm looking for an appropriate formula (google isn't helping) Thanks!

So this isn't a homework problem persay, it was given information but I just couldn't wrap my head on why this was true. We have 1-d heat transfer through a planar slab. If we have a T_a for the temperature outside, then as we T_1 for the temperature on one end of the surface, and T_2 for the...

Homework Statement Consider a brick wall, 4.0 m high, 6.0 m wide and 300 mm thick, where the thermal conductivity of the brick is 0.8 W.m-1.K-1. During a particular one-hour period, the temperatures of the inner and outer surfaces were measured to be T1 14oC and T2 6oC respectively. The...

I'm hoping to start a simple heat transfer model. It's basically a cylinder filled with air at a temperature T=300K. The bottom wall of the cylinder, made of steel, is heated (and kept at the constant temperature of T=400K). The side walls and top for the moment are treated as adiabatic (since I...

Homework Statement << Oversize image deleted by Moderator >> From this problem statement I am to find the heat transferred to the oxygen stream and the hydrogen stream. Homework Equations q''_0 = q''_oxygen + q"_hydrogen The Attempt at a Solution I first drew a thermal...

Im working on a little project where I am attempting to generate steam from a hot gas pipe. I haven't measured the rate of flow or temperature of the fluid as of yet, and I haven't decided upon the choice of material, but I'm looking for some calculations to start. My plan is to wrap a water...

Assume that there is a original wall which does not have any defect inside. After an excitation of heat at one side of the wall, Ti is 37°C and To is 30° C. Thermal capacitance is assume 1. So the heat transfer is 7. For another condition, i want to find out if the wall has air pocket inside...

Hi There. I'm currently working on a design project for school. Basically its a plate chiller which is lowered into a pot of hot liquid. The plates have channels in them thru which water will flow, the result being cooling of the hot liquid in the pot. I've done a lot of research and...

You place 1.0 kg of ice ( at 0 deg c) in a pot and heat t until the ice melts and the water boils off, making steam. How much heat must you apply to achieve this? Also, a printing plate of 20 kg is made of lead. After casting, the solid lead cools to 90 deg c . It is then dropped into a...

hi I am new here a query about heat transfer- there are layered walls with different conduction coefficient. the last layer is maintained at freezing point while the first is at room temperature my question is will the ice not melt at the last layer considering that its temperature is...

Hey, I was doing some revison for a test and i came across this question which I can't get my head around a clyndrical copper block, 0.3m in diameter and 0.4m long is initially at a uniform temp of 60°C and half its curved surface is exposed to a heat flux of 450w/m^2. If the complete surface...

Homework Statement A fire fighter (approximated by a two-sided black surface at 310 K 180 cm long and 40 cm wide) is facing a large fire at a distance of 10 m (approximated by a semi-infinite black surface at 1500 K). Ground and sky are at 0 °C (and may also be approximated as black). What...

hello I need help regarding a small project on thermoelectric refrigerator. I need to cool a 5.4 ltr capacity refrigerating space to maintain it at 10-12 degrees. I have the cooling module in place.I needed to dissipate 98 W of power from one module via a heat sink. I have a heat sink that...

Hello, I'm not actually asking a homework question. I'm working at an internship and have been asked a practical question about how long it will take a steel rod to change temperatures. Homework Statement Because it's not a problem from a textbook, I may not have all the required data, but...

Alright, chemistry student here. No previous experience with these types of problems. Doing an interdisciplinary student project where we have to insulate a thin aluminum wall. http://i.imgur.com/8ztNq.gif We have a x=5mm thin aluminium wall used for dividing two air flows. T1=308 K and...

Homework Statement When an immersion glass thermometer is used to measure the temperature of a liquid, the temperature reading will be affected by an error due to heat transfer between the liquid and the thermometer. Suppose you want to measure the temperature of 10 mL of water in a Pyrex...

Homework Statement A copper rod of length 0.20 m and cross-sectional area 6.00 10-2 cm2 is connected to an iron rod with the same cross section and length 0.28 m (the figure below). One end of the copper is immersed in boiling water and the other end is at the junction with the iron. If the...

I tried searching for this but i couldn't find an answer so i hope this is hasn't been discussed and if so - sorry- and id appreciate a link.. Here we go: Lets say we have to glasses, A and B. In glass A we pour boiling water and add milk straight afterwards. Now for glass B we pour the...

Homework Statement A resistance, connected to a battery, is put inside a thermally insulated cylinder which has an adjusted frictionless piston and contains an ideal gas. Through the resistance, a current i = 240 mA flows. At which velocity v should the piston move upwards, so that the...

If an area of 1 m2 at the Earth surface emits Q/t = 54E-3 J/s in radiation, what would the temperature at the Earth surface be, if there would be no other energy sources? Assume that the Earth is a perfect black body emitter (e = 1). Q/t = e(5.67E-8)(A)T4 54E-3 = 1(5.67E-8)T4 T = 31.2 K? The...

Hello I am trying to validate my model by comparing a simple axisymetric 2D impacting flow of air on a surface. The geometry is simple: a cylindrical (diameter d=26.5e-3[m]) jet of air (debit Speed Ud=13.46[m/s]) is impacting a surface at distance H=0.2833[m]. Flow temp is Tj=20°C Wall...