Questions tagged [thermodynamics]

Questions relating to the various laws of thermodynamics, transformation or movement of a form of energy to another form, primarily but not limited to heating or cooling of a fluid.

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How does humidity, specifically using a humidifier, affect the filtration of PM2.5 particles from a room?

I live in a very smokey and dry area where people are advised to use air purifiers. Since it's also dry I'm curious what affects, if any, adding a humidifier to a room with an air purifier would have? ...
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Gaps in derivation of thermodynamic property equations

If $h=h(T, P)$. Does $ dh = c_pdT + \left[v - T\left(\frac{\partial v}{\partial T}\right)_P \right]dP \Rightarrow h_2 - h_1 = \int_{T_1}^{T_2} c_pdT + \int_{P_1}^{P_2}\left[v - T\left(\frac{\partial v}...
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How to compute heat produced by 2.5kw heating element

Lets say the following is limited to 2.5 kW only and the thermostat and flow switch failed during use. After water is boiled away and bit of steam released. What would happen to the heating element ...
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at what point is increasing pressure ratio diminishing in returns?

piston engines of ww2 planes had pressure ratio of at least 10, while jet engines were still vastly superior with a pressure ratio of only 3. Certainly pressure ratio of 1 would bring 0% fuel ...
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1answer
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Determining the final surface temperature and final gas temperature flow through a tube in a room

I am trying to calculate the final temperatures as stated above. There is hot gas flowing through a tube that is insulated and inside of a room (no wind). I will try to walk you through my thought ...
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Hydraulic lift connected to two pistons

I just finished a problem, and got the correct answer, however I am confused on one of the mathematical operations that must be performed in order to get the correct answer. The problem is as reads: ...
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Where would I find tabulated values for thermal conductivity of refrigerator gaskets?

I'm trying to calculate heat flux into a refrigerator through the gasket that seals the door. I'd like to find the thermal resistivity or conductivity of the gasket, but it seems like there aren't any ...
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34 views

Why do high pressure multistage air compressor have different piston diameter sizes? [closed]

I meant like this kind of compressor https://www.bauer-kompressoren.de/fileadmin/_processed_/csm_compressor-block-junior2_b92a76a02e.jpg also would the compressor reach high pressure if the diameter ...
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Is it just surface area alone that causes bridges to freeze?

Scenario: Object 1, a bridge freezes over do to the surface area exposed to the below freezing air. Object 2 has the same surface area exposed to the same air, but its base sits on the ground that is ...
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Time-rate of change of P and T in a pressurized rigid volume with a hole in it

I am trying to model the time-rate of change of pressure and temperature of a gas being held within a pressurized rigid volume as it escapes: an unsteady, open system with no heat transfer. Most ...
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1answer
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What is a thermodynamic process that is not polytropic?

In discussion under another question, it was pointed out: "Not every process is polytropic; that is just a special case when $pV^n$ is constant" Must have missed that in school. What is a ...
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If you have a small fan that blows hot air, and a larger fan that blows cold air against it, what happens to the hot air?

For context, I have a laptop that has a fan that sucks in cold air from the top on the left side (for cooling the cpu), and a fan that blows hot air out the bottom on the right side (for cooling the ...
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Water Cooling a Personal Computer

I intend to water cool my next PC. There are three areas of heat production in a PC - the CPU, the GPU and the motherboard itself. Would it be more effective to treat these three areas separately (...
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Most efficient orientation of exhaust vents on top plate of chassis for air flow with regard to heatsink fins?

I'm looking for some advice from an ME or anyone who understands heat transfer,convection, etc. I'm currently laying out in Inkscape a top panel for an audio amplifier I'm building. Now, my question ...
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1answer
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Has anyone built a heat powered vapor compression cooler?

I've had this idea in my head for a refrigeration cycle which is powered by heat, uses only one fluid, and whose only moving part is the fluid. I would like to know if my idea is new, or if it's ...
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Heat loss calculation and Energy Balance

The image shows the CAD model of the annealing zone in a galvanization simulator. The zone is electrically heated with a AC current of 5597A at 2.09V. This whole zone is surrounded by insulating ...
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Can I calculate the amount (mol or mass) of water in a gas, in a heat exchanger, if I know the partial pressure of the water?

Is it possible to calculate the amount of water (mol, mass...) in a gas, in a heat exchanger, if I know the partial pressure of the water? The stream through the tubes is mainly benzene and ...
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Work done by compressor to fill a tank

A reciprocating air compressor is used to fill rapidly a $3m^3$ tank at $30°c$ and $1\ bar$. The filing process is governed by $pv^{1.4}=constant$. The effects of kinetic energy may be neglected. The ...
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Determining the heat capacity of an X-Band transmitter

I am conducting a thermal analysis of an X-Band transmitter that will form part of the payload in a CubeSat. The goal is to determine how long the X-Band transmitter can operate before it will ...
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1answer
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calculating energy usage with measuring the temperature

I am an electrical engineer working on a project. My goal of this project is to make an IoT solution where I continuously measure the temperature of room in a building. I want to calculate the amount ...
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2answers
25 views

What is the purpose of combustor in a gas turbine

I have read online that a gas turbine converts the chemical energy in the fuel gas to mechanical energy of the turbine blades. The way I see it, because of this hot air one would have to go for heat ...
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1answer
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Simulation of temperature in insulated box

I have a box outside that I want to insulate such that the temperature inside the box doesn't drop below 10°C given outside temperatures of (in the most extreme case - at night) -10°C. Inside the box ...
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Advantages of hydrogen gas turbine over fuel cell

In the setting of large-scale electricity generation, I was wondering why one would want to burn hydrogen in a gas turbine instead of using it to power a fuel cell. Aren't fuel cells more efficient ...
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How is the kinetic energy change during a throttling process negligible?

The throttling process is a constant enthalpy process, in which the pressure decreases. So, h1 = h2 u1+p1v1 = u2+p2v2 If the pressure is decreasing and if we consider the Joule-Thomson ...
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Clarification on specific heat of materials

At a temperature of 25 °C, the heat required to raise the temperature of 1 kg of water by 1 K is 4179.6 joules, meaning that the specific heat of water is 4179.6 J·kg−1·K−1. Does this also mean that ...
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Working of air conditioner

I want to understand working of AC at a basic level. Hence following is my question. Let there be a closed room of volume V at indoor temperature $T_1$. It has to be cooled down to temperature $T_2$. ...
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Is it more energy efficient to use cloud storage or connect a raspberry pi to an external hard disk? How can we quantify this?

I am thinking about where to store my digital files for backup. I want to have the lowest carbon footprint. (I'm going to use energy usage as a proxy for carbon emissions to make the problem simpler.)...
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Ideal Exhaust velocity of a rocket nozzle

In a youtube video, they defined exit exhaust velocity of a rocket nozzle as $$v_2 = \sqrt{\dfrac{2k}{k - 1}RT_1 \left[1 - \left(\dfrac{p_2}{p_1}\right)^{(k - 1) / k}\right]}$$ How can I derive this ...
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How far can we compress air manually?

I am not sure if such devices even exist, but I'm sure we can improvise. A device in which we could (manually) turn a shaft, screw a screw, or hammer an air-tight follower into a strong walled ...
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What will be the irreversiblility for the overall process

Air enters an adiabatic compressor at atmospheric conditions of bar. 15 and leaves at 5.5 bar. The mass flow rate is 0.01 kg/s and the efficiency of the compressor is 75%. After leaving the compressor,...
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How can I calculate the airflow needed for a fan to cool a system?

The airflow needed for a system to sustain itself at 80°C with 25°C ambient temperature can be calculated with this formula: ...
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How effectively will this evaporation setup cool down the water?

I devised a setup, and I show it in the diagram below. Suppose I have these specifications: Water in the bottle is 5 liters and it's initial temperature is 28°C. The bottle capacity is 6 liters. The ...
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When does Q = m(h2 - h1) hold true?

From the first law of thermodynamics: $$\Delta U = Q_{12} - W_{12}$$ where $\Delta U = m(u_2-u_1)$, $W = p(V_2 - V_1)$ with constant pressure, and $Q = m(h_2-h_1)$. In the energy rate form of the ...
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Enthalpy-Internal Energy Conservation in an Open System

In preparation for the FE, I've come across a thermodynamic scenario in Michael R. Lindeburg, PE's review manual that I cannot seem to wrap my head around. Though I have a full solution to the ...
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Thermodynamics, how can i do this with steam?

I have a problem with thermodynamics. I have this question: $q_{12} = ?$ Steam heating in constant volume. $p_1 = 1.76$ bar. Steam quality: $x_1 = 0.7$; $T_2 = 200$ Celsius. Where ’1’ is the current ...
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Maximum work from the process

Problem statement: 2 kg of air at 500 kPa expands adiabatically in a closed system until its volume (V) is doubled and it's temperature become equal to that of surrounding which is at 100 kPa, 5°C. ...
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1answer
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Melt plastic powder bed with radiant heat?

I want to melt a bed of plastic powder so that the powder bed once melted and then cooled forms a solid sheet of plastic. In order to melt the powder I'm thinking of passing a nichrome (Ni80/Cr20) ...
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How to measure and create PVT diagram

We have all seen PVT diagrams. From my understanding one should measure pressure, volume and temperature on or near the outside of the system. Volume: maybe by displacing water initially and then ...
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1answer
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Fully saturated liquid and vapour

In terms of fully saturated vapour and liquid for water. Why in a real world heat pump cycle for example may the water not exactly reach these saturation lines as indicated in an ideal cycle?
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How to measure the power output of a stirling engine

I'm doing a project for thermodynamics where I have to measure the power (work over time) of a Stirling engine for varying temperature differences. I don't necessarily need an exact answer (as in: ... ...
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How does the Xbox Series X “Heat-sink chassis” work?

I understand what a heatsink does, but I cannot wrap my head around how the newly announced Xbox Series X's heat-sink chassis works. From Xbox: Heat-sink chassis A heat sink is a non-electronic, ...
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What is the specific heat capacity of corrugated cardboard?

I am testing out different materials with different specific heat capacities and their correlation with soundproofing (e.g. wood, cork, styrofoam, etc.) but I can't seem to find the specific heat ...
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Reference book for hydraulic systems design

I'm looking for a good reference book on the topic of fluid dynamics/hydraulics systems engineering. I'd like a reference for simlpe/estimate calculations on things like major losses (pipes), minor ...
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Can Peltier Modules be practically used to cool a room?

I am thinking of building a indirect Peltier AC to cool a room of approx size 30m3. Single/multiple peltier modules will be used to cool a insulated box with water inside. The box will be kept outside ...
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Heat Transfer Problem , 1 Dimensional Conduction Extended Surfaces

enter image description here So I am having issue solving this problem, I solved one part by the fact that in the given distance of 2L , 2 tubes are involved so I can find the heat conducted per unit ...
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How can water mist lower a room's temperature?

Let me start off by saying that this is strictly NOT a homework question, so before you mark it as "homework", think. I was looking at how the water cools my body when it evaporates off it. Then I ...
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Calculation for lowering temperature in a room… room-fridge with water mist?

I was looking at how the water cools my body when it evaporates off it. Then I thought the specific heat capacity could be used to calculate how much energy (i.e heat) would be taken out of a room ...
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How do you calculate heat transfer due to solar radiation for a multi-layer wall given the incident solar radiation and wall specs?

Trying to come up with a MATLAB code for calculation of heat transfer due to incident radiation on a building's walls, would the solution involve using the conduction equation only? What would be the ...
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1answer
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Stirling Engine Cooled Engine

Could a Stirling Engine replace the cooling system of an engine? Instead of having a clutch and fan attached to the main drive shaft to cool an engine, could a Stirling Engine and clutch share that ...
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Energy calculations for steam turbine

I am a civil engineering undergraduate. I have an interest in Biotropic Design and sustainable energy and am working on a new conceptual design. I would like to know what analytics may be done to ...

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