Questions tagged [heat-transfer]

Questions relating to the transfer of heat via the mechanism of convection, conduction, or radiation, in forms of systems (or your device) attempting to obtain thermodynamic equilibrium with another system (the environment or your other device)

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17 views

How to calculate the two parameters in the red box about Required ventilation rate and Calculated CO2-loss?

I dont know how to calculate the two parameters.I think The total energy of the light is 700w/m2*3600s=2520Kj,then I will not do it.
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15 views

Relationship between Heat Flux and Engine RPM

I'm doing a project that involves knowing the average steady-state heat dissipation rate of a single cylinder air-cooled engine (through the engine wall and fins) at a given RPM. The problem is that I ...
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28 views

Average Nusselt number or heat transfer coefficient to compare better heat transfer?

I'm simulating different arrays for cylinders in a simple cross flow heat exchanger (cylindrical pipes) as shown below: Inlet temperate(300K) is constant and the cylinders are at constant temperature(...
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Heat transfer and rise in temperature

Consider an object of mass M and specific heat C, and initial temperature T1. Let energy is transferred to the object at the rate of W watt. I want to calculate temperature of the object at time t. ...
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26 views

Heat sink Design

I have a problem where there is an 80 Watt thermal load that needs to be cooled to maintain 80 Celsius. The base of the heat sink is 5" x 7" and is oriented vertically with cooling via natural ...
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18 views

Final temperature of an isolated vessel - Thermodynamics

8) Consider an inextensible tank of 10 m3 of volume, isolated by an adiabatic wrap. The tank contains nitrogen at 2 bar and 300 K. This tank is connected to a piping by which more N2 (at 300 K) is ...
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14 views

When Convection exceeds radiation loss

A very hot small metal cylinder of mass, 50 g and surface area, 2 x 10^-3 m^2 , specific heat capacity, 500 J kg^-1 K^-1 and thermal conductivity, 25 W m^-1 K^-1 is to be rapidly cooled from 800°C and ...
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1answer
62 views

How do I determine the temperature inside a transformer vault?

I am trying to determine the temperature of an underground concrete vault buried 10m underground. The vault has the following dimensions: 2640mm x 5995mm x 2640mm with a wall thickness of 250mm. The ...
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Compute equilibrium temperature under a roof

I want to compute the equilibrium temperature below the roof (inside a building) to analyze the efficiency of an insulation layer. I impose the environment temperature $T_{env}$, the insulation layer ...
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45 views

Steam cycle for a boiler / radiator system vs Rankine cycle

Everything I've read on the Rankine cycle indicates that the feedwater pump is necessary for the cycle to work. However the steam cycle used in traditional household boiler / radiator systems seems to ...
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1answer
58 views

Wire heating and heat transfer in a cylindrical pattern

I have a series of copper coils with ¼” cooling plates between each coil. The cooling plates will be manufactured from aluminum and cooled using copper tubing. There are seven in series, and a plate ...
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76 views

Heat Transfer in Different Wire Configurations

I am trying to create a program which estimates the final temperature of a magnet made of copper wire. I have different configurations in mind, but I will start off with a straight square wire with a ...
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30 views

Heat Exchanger- the calculation of q

What is the heat transfer difference between parallel flow and counter-flow heat exchanger? Are different equations used to calculate q?
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Search for comprehensive term for plants with heat generation with heat storage and operating states

My master thesis deals with systems with several operating states that generate heat and store it in a heat storage. Thereby I analyze combined heat and power plants with combustion engines, but also ...
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104 views

Heat exchanger efficienccy

I'm thinking about a system that would replace water in a swimming pool with clean water from an Artesian well. The water in the well is about 1C and the swimming pool is around 20C. Reheating the ...
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1answer
22 views

Vertical vs Horizontal Ground Loop Heating

I'm wondering how to compare the efficiencies of vertical and horizontal ground loops for heating. [Assumptions follow, please correct if any are wrong!] The biggest differences seem to be the higher ...
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1answer
38 views

How to control precisely the wall temperature of a tubular reactor?

I have modelled a multi-tubular reactor performing a Fischer-Tropsch synthesis of alkanes and I was wondering about the stability of such a reactor. Even a very tiny deviation of the wall temperature ...
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46 views

Modelling reactor jacket with or without insulation, how to proceed?

I am currently trying to derive a model to help estimate as precisely as possible how much time can be saved by insulating the jacket of a reactor used for eating and cooling. EDIT: I edited my post ...
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53 views

Cooling Down Fridge Encased in wooden box

I'm currently working on a project which involves a small fridge encased in a wooden box. It's designed for hotels and the boxes vary slightly, but one common trait is that the box has an open vent ...
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31 views

Heat Transfer in A Cylinder of an Internal Combustion Engine

I am new in engineering, could anyone explain the approach to calculate the max heat generation, the heat transfer from the cylinder to the atmosphere and from cylinder to the piston. I am also ...
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How do you calculate the temperature after methane combustion if liquid H2O is sprayed into the combustor?

Calculating adiabatic flame temperature is pretty clear in thermo books, but how would you determine the temperature if liquid H20 was sprayed into the combustion chamber simultaneously? Thanks
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How to achieve successful Peltier cooling

I'm using a TEC12706 Peltier module for making a cooling setup. The hot side rejects heat to a Cooler Master Hyper 410R cooler and the cold side fin gets cold enough to form water condensate on itself....
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36 views

Thermal Non-Insulators?

I need a clear material that will allow sun in but won't insulate heat. Sun sun rays get in but doesn't trap heat. Any ideas?
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Sizing radiator

I'd like to do a DIY project to reuse my home AC heat output to heat my pool that is located very nearby the AC radiator. I planned on fitting a second radiator directly onto the heat output and hook ...
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27 views

Will a video projector submerged in mineral oil still work?

I’ve seen folks submerge computers in mineral oil to cool them- but would doing the same to a video projector profoundly throw off its internal optical aspects? I’m considering one of those small “...
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Help me Solve this Steady State 2-D Heat equation

So I tried to solve this PDE by separation of variables which was not applicable because of non-homogeneous nature of this PDE. Then I assumed ( after reading from a book ) : $$ T(x,y)=v(x,y) + \phi(...
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54 views

Calculating the Surface Temperature of a Cable with known heat flow

I have a cable which dissipates $\dot Q_{total}$ and I need to determine the surface temperature of the insulation $T_{ins}$ and the surface temperature of the conductor $T_{cond}$. There is an ...
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39 views

calculating the efficiency of a microwave oven

If I want to calculate the efficiency of a microwave oven, I have the input Energy (= power (watts) x time (s)) and the output which I measured using temperature difference (q=mct). So do I divide ...
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23 views

Determine Cp of an oil from density and temperature?

I suspect I know the answer to this, but hoping someone may know something I don't here. Is there a way I can determine the specific heat capacity at constant pressure (Cp) of an oil if I know the ...
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37 views

Characteristic length for the given problem of heat transfer

In the following problem of heat transfer, what does characteristic length actually mean? In this problem, they have found the heat transfer coefficient (h) separately for the vertical and horizontal ...
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Industrial scale heat pumps

I've read (1) that the efficiency (COP) of a heat pump does not change much with size. If that is true, why don't power companies employ them to produce yet more power from fossil fuels or renewables? ...
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37 views

Can radiant induction heat thermally decompose wood

Is it possible to thermally decompose an indicator like wood in a induction heating container made of stainless steel if the induction frequency is low enough to heat the container about 1000°c. ...
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31 views

Evaluating drag and convection for a flower heat budget model

I am currently in the process of creating a heat budget model to compute stigma surface temperature. Stigmas are part of the reproductive organ of a flower (which in my case are flowers of orchards). ...
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49 views

Calculating heath exchange for custom boiler

I am playing with the Idea that I should make a my own heath exchanger to generate warm water. But as a hobbyist I would like to calculate the potential of my design and here is the question for me, ...
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69 views

Boundary conditions in a heat transfer problem

One end of a small insulated rod is attached to a support which is maintained at a constant temperature of 473 K,and once the rod has reached a uniform temperature in its entire length the insulation ...
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49 views

Does a tank of liquid nitrogen increase in total internal energy after emptying?

Suppose there's a 10 liter perfectly-insulated sealed tank of saturated liquid nitrogen at 4 bar. Therefore the fluid has properties, $\rho=740 \,\frac{\text{kg}}{\text{m}^3}$, $m=7.4 \,\text{kg}$, $\...
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Developing a model of rate of cooling of steel tube in air

I am trying to develop an equation to determine the cooling rate of a steel tube in air. I'm using Fourier's Law, Stefan-Boltzman Law, Newton's Law as well as the specific heat capacity equation. The ...
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77 views

Does kettle shape affect the speed at which water boils?

Consider I have two type of cooking kettles, which the shape is just like a pure tube with the volume is 1000 cc (1 liter) with the radius and the height as below (volume=pi*r^2*h): The first kettle: ...
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64 views

Which is more important XY plane thermal conductivity or z direction thermal conductivity?

Im seeking an alternative to thermal grease/ pastes. I was researching graphite pads when I stumbled across the soft PGS line from Panasonic. I need to choose a suitable thermal interface material ...
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122 views

How to calculate the time to heat up a tank using recirculating liquid

My question is about a tank filled with some liquid (properties of the liquid are known and can be considered constant. Specific heat equals 1.5 kJ/(kg.K)). The initial temperature of the liquid in ...
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36 views

Calculating geothermal heat pump

So I need to calculate how big geothermal heat pumps I need for a building. Heat pump is used for heating and to heat used water. If I know how many kW's are needed for heating the building and the ...
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106 views

Save money with using a refrigerator correctly - blowing cold air to the back of it?

We are heating up our houses in winter to ex.: 21C to then have an insulated box inside the house, which we cold down to 5 and -15C, and we call it a refrigerator.. :) The situation: we would buy a ...
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39 views

Absorbing heat from a surface

I have a cold body of constant temperature A and a hot surface several times it's area. What is the best way I can absorb the heat from that surface using A. Will sheets of metal like alluminium or ...
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Why are home geothermal systems usable anywhere in the U.S. but industrial geothermal plants limited in geographical use?

Geothermal systems are used in regions across the U.S. for home use, but industrial geothermal plants are only used in areas where subteranian temperatures are very high. Why is this? https://en....
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DIY Thermal Solution [closed]

What would be the best way to design a sealed computer containing a gas or liquid circulated by a fan/pump to cool the components? ( With a metal case ) Then the computer would not be susceptible to ...
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49 views

Air Cools As It Expands

What is the degree of cooling caused by air flowing from smaller diameter into a large diameter? How much does air cool as it expands? If the air inlet was the biggest hole on the right and the ...
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Please help solve this problem! [closed]

Fluid with mdot = 0.025 kg/s and Tm,i = 25oC is flowing through a long metal cylindrical tube where the diameter is 0.032 m and the length is 2 m. The surface of the tube is heated with a heat flux of ...
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43 views

Peltier Element - Segregation of the Hot/Cold

Referring to this diagram: How does the height of the P and N components affect heat or cold generated on this thermoelectric element? The idea I keep having is that it seems like the hot and cold ...
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1answer
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Connect heated copper tube in PVC tube

I have a copper tube that I'm heating (quite a lot) with a torch, I have to connect a PVC pipe in the entrance of the copper and one in the exit (so water can flow through the copper pipe). The only ...
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Temperature not changing in my code for 1-D heat equation: Explicit Scheme

I am trying to solve the following 1-D heat equation with provided boundary conditions using explicit scheme on Matlab. I have been trying to plot the results but I realized that my temperatures are ...