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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Significance of Radiation in Heat Transfer Problem

I am trying to calculate the significance of radiation heat transfer to a fluid for a particular geometry I am modeling in Ansys. I would like to leave out radiation in the model, but I want to ...
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Best metal for solar energy collection in an evacuated tube solar water heater

I am building an evacuated tube array for a solar water heater and I am selecting the materials to use for the tubing and the collectors (the places connected to the tubing that help absorb the solar ...
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Identify this textbook

I would really like to buy this textbook, but only see a scan of one chapter online. Could anybody help me identify the book? Thanks!
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How to compute wall heat flux q with just wall temperature

I am doing some simulation for natural circulation loop and have a heat rate q in the heating leg and a fixed temperature for the cooling leg. I know the heat rate for the heating section (128 W) and ...
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What would be the best setup to evaporate as much seawater as possible using the propane from a 1kg tank?

Out of curiosity, What would be the best setup to evaporate as much seawater as possible in using the propane from a 1kg tank? Will it be, Big pan, boil them all at once Small wide pan, boil them a ...
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43 views

Examples of two dimensional heat conduction problems

Can anyone give me some examples from real life, where the heat transfer can be modelled as two dimensional. Also if one could explain why we can model it as 2 dimensional.
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Is there a way to make an air conditioner without venting heat outdoors?

Is there a way to make an air conditioner for when you can’t vent the heat outdoors? Can you trap the heat in an object or convert it to another form of energy? For example, could you transfer the ...
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1answer
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Pre requisites for a course in Heat Transfer from Fluid Mechanics , for a Mechanical Engineering Bachelors Degree [closed]

Can anyone please tell me the topics I need to study from Fluid Mechanics, specially fluid dynamics to understand Heat Transfer in a better way?
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Can aluminium foil be a thermal insulator?

I've searched on Google that aluminium foil can be a thermal insulator, but how does it work? From my thought process, it should've been a conductor because its a metal, right? But, some said that ...
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Thermal conductivity and the second law

I am having trouble figuring out the solution for part d. Can anyone give me a hint?
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Question regarding evaluating 1D heat transfer PDE

My question regards cooling of an object using 1D-heat transfer with fixed surface temperatures. First I need to find the solution to this PDE: Based on the conditions, I worked out that the ...
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How would a realistic PV diagram look for a Beta-Type Stirling Engine?

Normally, most textbooks use the diagram below to describe an ideal Stirling Cycle. 1st comes isothermal expansion of gas, 2nd comes isochoric heat transfer to the regenerator, 3rd isothermal ...
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3answers
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How do you imagine momentum?

If you want to explain it to a layman (who belongs to the science stream ofc!!) how do you explain it? Also, what is momentum transfer when it comes to fluid mechanics?
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Why do we consider a wavelength range when defining spectral emissive power of a blackbody?

The spectral hemispherical emissive power of a blackbody is the amount of thermal energy emitted in the form of EMW lying in the wavelength range of $\lambda$ to $\lambda + d\lambda$ via thermal ...
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Maximum rate of heat transfer in a balanced counter flow heat exchanger in NTU method

In effectiveness NTU method for heat exchangers, we have effectiveness of the heat exchanger defined as $$\epsilon = \frac{Q_{actual}}{Q_{max}}$$ Where $$Q_{max} $$ is the maximum rate of heat ...
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Improving ac efficiency in car

I live in Oklahoma. HOT in summer. I drive a small car. Honda Fit. Seems to me, a smaller cabin would cool faster than a larger one. If I "made my car cabin smaller," would the ac work ...
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1answer
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In this scenario, if I continue to increase the length of heat exchanger how will the temperatures change?

Consider a counter flow double pipe heat exchanger inside which the cold fluid enters at 20 degrees Celsius and hot fluid enters at 100 degrees Celsius. Initially the length of the heat exchanger is ...
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1answer
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Maximum rate of heat transfer in Effectiveness NTU method for a heat exchanger

The effectiveness NTU method is used for determining the heat transfer rate for a heat exchanger, with known inlet temperatures and surface area. It makes use of effectiveness which is defined as $$\...
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Homemade spray dryer - how to generate powerful hot air?

I am currently trying to create homemade spray dryer, Which is basically pumping hot air in a chamber where targeted liquid is sprayed, so that the water content could instantly evaporate, leaving ...
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1answer
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Arithmetic and Log mean temperatuer difference of a double pipe heat exchanger with parallel flow

Consider a double pipe parallel flow heat exchanger, the mean temperature difference in this case turns out to be logarithmic because the temperature profiles are exponential. If we would have made ...
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How to model a condenser (heat exchanger) where both streams are two fluid mixtures?

As mentioned I would like to model a heat exchanger (using Python). In this case, the condenser/hx streams are both a mixture of O2 and N2 These are known for both streams: Inlet temperature Inlet ...
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Why does thermal conductivity of a pipe matter in a double pipe heat exchanger?

My understanding is that thermal conductivity is responsible for the time until something will heat up. For example, if you hold a copper bar over a candle it will quickly become hot at the other end. ...
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2answers
109 views

Aluminum or Copper, which one is better to control and maintain the temperature?

Friends, I am an EE/SW/Controls eng. Please, pardon me of perhaps incorrect terminologies. I am working on a R&D project: A chemical lab equipment has a 2" long metal pipe enclosed in ...
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86 views

How are heat exchangers normally calculated?

Most of the calculations that I find in books are about calculating the heat transfer rate, which I'm not sure why I would care about. What I imagine is the case in a real world situation is that I ...
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1answer
47 views

In a shell and tube heat exchanger, does reducing flowrate affect the outlet temperatures?

Let's say I have 2 exchangers that are completely the same, only difference being that one of them has half the number of tubes. Also let's assume the coolant is the same and has the same inlet ...
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Trying to find the steady state temperature of air inside a semi-truck trailer?

To start, this is mostly a procedural question, so I'll be doing some handwaving for the numbers. Lets say I have a semi-truck trailer. It's insulated and refrigerated, and meant to transfer drink ...
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1answer
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Out of the three types of Stirling Engines, which one is the most efficient and delivers the most amount of power?

I was thinking that the beta Stirling engine would be the most efficient as it has a displacer to block heat transfer from the hot to cold regions in between thermodynamic cycles. However, I heard ...
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1answer
50 views

Equivalent Resistance Between Two Points in a Wye Network

I am interested in learning how to calculate the equivalent resistance between two points in a wye circuit for application to thermal networks (i.e. I'd like to calculate the equivalent thermal ...
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1answer
70 views

In case of solvation , Who converts gaseous ions to aqueous ? Why do we even have gaseous but not solid ions?

We take Nacl and dissolve it in water. There is formation of $Na^+$ and $Cl^-$ gaseous ions along with 2H+ and $Cl^{2-}$ aqueous ions. Then , Na+ is attracted towards $Cl^{2-}$ and 2H+ is attracted ...
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Cold Plate Thermal Resistance

I am designing a cold plate that will have 4 Power Modules Mounted on it. The total power loss from the modules is 5000W(1250W per Power Module). I have simulated the results on ANSYS Fluent and ...
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2answers
53 views

How to visualise/measure airflow in sauna?

I'd like to visualise/measure the flow of air in sauna to optimise the ventilation. Is there a way to colour the air (non-toxic!!!) so I may watch the flow? Or is there any other accessible technology ...
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2answers
64 views

What are some technical problems with generating electricity using a gas turbine or combustible engine at a gas flaring site?

Numerous oil and gas exploration sites practice flaring for safety and disposal of unwanted low calorific gases. However, instead of just standalone burning the gas, why can't a gas turbine or ...
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Do all thermoelectric generators (TEG) require two distinct metals?

Most thermocouples that I've seen being sold online consist of two separate metal wires connected at junctions. Many smaller thermoelectric generators consist of a combination of iron and copper or ...
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Mathematical derivation for 1st law of thermodynamics

Mathematical derivation for 1st law of thermodynamics : What I know : 1st law of thermodynamics is known as or derived as the conservation of energy . But how are the terms U , q and W derived from ...
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Difficulty in understand the meaning of standard enthalpy of formation

Standard enthalpy of formation is when one mole of compound is formed from its constituent elements. Example : $H_2$(g) + $O_2$(g) —>$ H_2O$(L). But we don’t say the same for $CaO + CO_2$ —> $...
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What is a safe and efficient temperature range for absorption chiller generators?

I've read that the role generators play in the absorption chiller cycle is to concentrate the salt solution so that the evaporator/absorber can maintain a vacuum by constant absorption of vapour ...
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1answer
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Can I consider this scenario for the phase change of $H_2O_{(s)}$ to $H_2O_{(L)}$

From a particular topic : Enthalpy changes during phase transformations. It says in my textbook that standard state of a substance at a specified temperature is it’s pure form at 1 bar pressure. Let’s ...
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53 views

Why ΔH has two separate equation in my textbook?

ΔQ = ΔU + Δ(PV) (First law of thermodynamics) which has the same statement as the 1st equation. $Q_p$ or ΔH= ΔU + PΔV which is the heat exchanged at constant pressure. Then why in the image above in ...
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4answers
506 views

Difference between temperature and heat

It is becoming very difficult for me to understand the difference between temperature and heat. About heat all I have read : Heat exchange is related to as exchange of matter + energy. Heat is ...
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1answer
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What is heat , chemical energy and thermodynamics laws restrictions

Below is a text over which I have my questions which I have written below this text: Chemical energy stored by molecules can be released as heat during chemical reactions when a fuel like methane, ...
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Why does temperature not increase by putting more logs into the fire

Why does temperature not increase by putting more logs into the fire ? It is a very common observation which I have seen but after some research online I found that it is not completely true. One ...
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2answers
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Difficulty in understanding the scenario for this Q

Q:If a closed rigid wall container filled with 20 gm of He moving at a constant speed of 10 m/sec is stopped abruptly to stand still, find the increment in temperature of this He sample. My question ...
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1answer
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Net rate of heat transfer of venting air into another room?

I have a portable air conditioner, but I don't have a window in my room. I'm only gonna be here for about 2 more weeks, but the temperature is in the 80s/90s, and I'm very sensitive to the heat that ...
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1answer
60 views

How to transfer air heat easily?

Assume two buildings, one which generates a lot of air heat inside due to electrical equipment running etc. The buildings are 20-25 meters apart. Some questions: How can one easily transfer heater ...
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1answer
41 views

Do throttling devices need valves?

Why is it that a throttling device always has a valve leading to it? If in a closed system loop, a cooled gas exists right before the throttling device, shouldn't the sudden decrease in cross-...
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1answer
94 views

How does steam in almost vacuum condense at 35 Celsius?

I read about absorption chillers and found out that the water is evaporated/boiled off at the generator. Water boils over at about 3.7 Celsius in the near-vacuum conditions in the generator. Now the ...
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1answer
45 views

Absorption chillers: can they achieve temperatures below zero Celsius?

If I understand correctly (history shows I probably don't), then the only reason why the absorption chiller evaporators are restricted (I hope that's the right word) to extract just enough heat so the ...
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Solidworks flow simulation temperature drop

Using Soldiworks flow simulation, I want to calculate the temperature drop of water (40 degrees) which flows in 10 m steel pipe. How should I manage Wizards setting and goal?
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2answers
78 views

Boundary conditions at interface for1D transient heat conduction problem in cylindrical coordinates

The problem I am currently working on involves rapidly cooling liquid aluminum in a cylindrical graphite crucible and getting the radial temperature distribution over time, possibly using finite ...
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1answer
34 views

Why is potential energy = 0 for ideal gases and not for non ideal gases?

Why is potential energy = 0 for ideal gases and not for non ideal gases ? The reason is in my textbook that average between the atoms increases or decreases due to bonds being broken.So , my Q is that ...

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