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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45 views

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
43 views

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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26 views

Heat transfer Calculation for heating polypropylene plastic Nano tubes

I am from electronics background so I don't know much about heat transfer calculation . I am designing PCR thermal cycler which will provide Quick heating and cooling to the solution in the ...
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1answer
33 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
68 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
41 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
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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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3answers
102 views

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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1answer
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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
29 views

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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1answer
49 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
499 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
41 views

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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5answers
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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
48 views

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
42 views

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
39 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
38 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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0answers
19 views

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
65 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
32 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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1answer
70 views

How much water do steam turbines consume per kWh of electricity generated?

I know this depends on some factors, and I can only think of these: the inlet steam's temperature and pressure. If there are more factors then please do tell me. What is the maximum figure in liters ...
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1answer
67 views

Does adding cold water to evaporative air coolers actually produce colder air?

Or should it be the other way around, because hotter water evaporates easier than cold water? I know this sounds stupid, so just hear me out. I use an evaporative cooler and add normal room ...
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32 views

Heat Transfer FEA with matlab

I have to write a matlab code using finite element method to solve this problem. I have solved it as follows but I dont know how to apply it in matlab. I have to write a matlab code using finite ...
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1answer
63 views

How to graph a dimensionless ratio as the parameter on an XY graph? [closed]

We conducted an experiment to determine the relationship between the heat transfer coefficient for forced convection over a cylindrical rod due to varying air flow velocities. The relationship that ...
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1answer
19 views

Calculating final temperature of humid air and cool stone

I'm trying to gauge the efficiency of a night-cooled stone to condense water from the humid air at seashores at noon. I'm assuming the stone is thermally insulated once it's in thermal equilibrium ...
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0answers
25 views

Find the irrigation pumping rate (mass flow rate of a pump) versus time

Here is what we are given. Time ranges from 0 to 10 hours, with t=5 being solar noon. $\dot Q = 90Asin(\pi t/10)$ Watts, where A is the solar collector area in square meters and t is the time after ...
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26 views

HVAC Condensor Liquid Level/Ratio Estimate

Let's say I have a simple condenser inside of a HVAC system with 1 point of entry(Super-heated Vapour) and 1 point of exit(Saturated Liquid) for my refrigerant r134a. A pipe passes through it with ...
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1answer
53 views

Does a Peltier device conduct heat when turned off?

If I put a Peltier device between a heat source and a heat sink (Peltier turned off), How well will it conduct heat? as opposed to lets say a copper block? Thank you
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2answers
71 views

How do I calculate final equilibrium temperature of a pot of water on a stovetop vs. after I add food to it?

So I'm trying to come up with a simple hack to heat up food in a water bath to hopefully +-1ºC of a target temperature, but I really don't understand the physics of it all so much. I'm pretty sure I ...
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3answers
89 views

I want to dissipate 3 kW of heat with an air conditioner. How big of an air conditioner do I need?

So the title says it all. I have a room (4 m x 4 m x 2.5 m) which is closed.(Actually there is a window and I could add a 50 cm panel fan if needed as an exhaust if that will help.) I have some ...
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1answer
24 views

Heating an uninsulated campground building with high ceiling and radiant floor in New England

We have a beautiful dining hall designed for summer camp use, which we want to keep warm enough for group activities in the winter. The chosen heat is radiant floor, hoping to keep temperatures ...
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1answer
41 views

Can't tesla turbine work on air heated by solar concentration? [closed]

If we heat air along a pipe that's tilted at 30° to the horizontal using parabolic troughs, the air should rise upwards (I'm not sure how fast or powerfully) and then connect the outlet at the top ...
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2answers
57 views

Why is Carnot Factor defined as 1 - (T(cold) / T(hot))

This is the proof I've found for the Carnot Factor: $$S = \frac{Q}{T} \qquad \qquad (1)$$ $$S_{in} = S_{out}\qquad \qquad (2)$$ Because entropy stays the same when ...
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Determining length of interstage cooling coils for removal of heat

I'm currently trying to determine the length of cooling tube required to remove a specific amount of heat from my exothermic reactor in stages. I'm aware I need to use the equation $Q = UA \theta_{...
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1answer
91 views

How to calculate heat loss across a process pipe with perpendicular air flow

My thermodynamics knowledge is extremely rusty, so I would appreciate some guidance on how to solve this problem. As illustrated here, I have a process pipe (steel) with a gas flowing through it (blue)...
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1answer
54 views

How to evenly heat stainless type 304 steel bar to approximately 200F?

I need to heat stainless bar stock prior to bending in a forming machine. I would like to reach approximately 200 degrees F. The material is stainless type 304/304L, 3/16" thick. We are heating ...
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1answer
34 views

Does a photon impart energy on a surface (to raise its temp) if it goes THROUGH that surface?

Hi so I have this senior design project involving cooling human skin as it is irradiated by an infrared LED. Human skin not only is super absorbent to IR, but that IR goes THROUGH the thickness of it ...
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1answer
19 views

How can we determine that the flow in a wind tunnel reaches the steady-state condition?

I am investigating the flow and heat transfer over a cylinder in a wind tunnel. I want to record the data that I need to calculate the flow characteristics, But how can I make sure that the steady-...
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1answer
47 views

How to compute velocity distribution in the developing boundary layer on the cylinder

Air flows perpendicular to the axis of a cylinder $a=1$ cm in diameter. Air speed upstream of the cylinder is $U=6.72$ mm/s and its kinematic viscosity is $2.1×10^{-5}$ at 350 K. I want to obtain the ...
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Optimizing flue gas temp for maple syrup evaporator

I have a simple maple syrup evaporator. Fuel is burned in a firebox located under 1mm stainless steel pans containing maple sap--which becomes syrup once enough water is evaporated. After passing ...
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2answers
113 views

Why does accuracy of temperature PID controller drop over time and how to eliminate it?

What am I trying to control? I have a container with approximately 3*2*6 meters (width, height, length). I am controlling through PID the ...
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1answer
60 views

Why do binary cycle geothermal power plants have so low efficiency?

Well, a binary cycle geothermal power plant utilizes the low temperature of the primary liquid to generate heat. I found out that they are only 10% to 15% efficient. Is the continuous flow of the ...
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1answer
43 views

Heat rate through composite wall with non-constant thermal conductivity

I just started a job working with cryogenics and I am trying to solve an interesting heat conduction problem that I was hoping someone could help me along with. I have a structure that spans from room ...
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How to calculate the ideal and realistic estimate of thermal efficiency of absorption chiller?

How Can I calculate the ideal and a realistic estimate of the thermal efficiency of the system (thermal, electrical and water) per 1 kWh chilling energy (removed from the chilled water)? What is the ...

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