Heat Definition and 1000 Threads

hello, im in bachelors mechanical engineering programme and my thermodynamics papers are in few days one question is related to heat exchangers or forced convection, but our professor has hinted that in the exam the question regarding heat exchanger, forced convection will be a case study of a...

hello. Simple question here for somebody just learning the basics. On the atomic scale what’s the difference between agitation and heat? For example, diluting salt in water. If you increase the heat of the water, more salt dissolves. Stirring it also makes the salt dissolve more too it seems...

There are three geothermal systems that are commonly used: sry steam, flash steam, and binary cycle https://www.eia.gov/energyexplained/index.cfm?page=geothermal_power_plants . What are the efficiencies of the plants from best to least effecient on average?

Homework Statement Homework Equations q = mCat The Attempt at a Solution I'm kinda confused the different between Hrxn and q? I know the reaction warms the water with q=mcat = 150*4.18*(59.5-20)=24766.5 J. This is the heat released from 1.25 grams of Ca which is 0.03 moles of Ca. But, the...

Greetings! I did the famous "Mass Lifter Heat Engine" experiment in which a mass is put at the top of a piston enclosed within a cylinder. The cylinder is connected to an aluminium canister of air and the air inside this canister expands and contracts the piston with thermal contact. We had 2...

Homework Statement Homework Equations q = mcat mols*hvap The Attempt at a Solution To decrease temp from 70 to 56 degrees (bp), q=mcat = 1195.5 to convert this gas into liquid , must do mols * hvap = 29129 joules to decrease temp from 56 to 0 thought, i get q= mcat = -7047 J (which is...

Hello. I am starting to learn about thermodynamics. (i'm going to use lower case "d" for delta) Energy is neither created nor destroyed. So dU = 0 for the universe as a whole. If the universe is constantly expanding, then it must be doing work on the vacuum around it, right? So W is a...

Looking to make a heat exchanger so that I can have a less than adequately antifreeze treated water (easily over 750 gallons, so very expensive) from the outdoor wood boiler constantly circulating through a water jacket, and heat an adequately treated fluid (glycol treated water) and can turn...

Homework Statement An office with a volume of 52.5 m^3 uses a heat engine that outputs 1200 W. Suppose that, initially, the office has a pressure of 1 atm and 20 degrees Celsius before the heater is turned on. After 10 minutes (6000 seconds), what is the final air temperature? Homework...

Homework Statement I am having an issue, not with the maths but with the boundary conditions for this question. A bar 10 cm long with insulated sides, is initially at ##100 ^\circ##. Starting at ##t=0## Find the temperature distribution in the bar at time t. The heat flow equation is...

Homework Statement A copper pot with a mass of 0.500 kg contains 0.170 kg of water, and both are at a temperature of 20.0°C. A 0.250-kg block of iron at 85.0°C is dropped into the pot. Find the final temperature of the system, assuming no heat loss to the surroundings. Homework Equations Q =...

Homework Statement A thin electrical heater is inserted between a long circular rod and a concentric tube with inner and outer radii of 20 and 40 mm. The rod (A) has a thermal conductivity of kA = 0.15 W/(m*K), while the tube (B) has a thermal conductivity of kB = 1.5 W/(m*K) and its outer...

Homework Statement show ## \rho c_m \frac{\partial T}{\partial t} = \kappa \frac{\partial^2T}{\partial x^2} -\frac{2}{a}R(T)## where ##R(T)=A(T-T_0) ## a) Obtain an expression for T as a function of x for the case of an infinitely long rod whose hot end has temperature ##T_m## b) Show that the...

Homework Statement What is H, the rate of heat absorbtion by an air conditioner with an EER of 8.3 that operates at 1800 W? Recall that 1Btu=1055J. Express your answer in joules per minute. Homework Equations H/P=EER The Attempt at a Solution H=EER*P H=(8.3 BTU/HR/W)*(1800 W) H=(14,940 BTU...

Homework Statement One cylinder in the diesel engine of a truck has an initial volume of 640 cm3. Air is admitted to the cylinder at 30°C and a pressure of 1.0 atm. The piston rod then does 500 J of work to rapidly compress the air. What are its final temperature and volume? Homework Equations...

Homework Statement So, my textbook doesn't go over these type of problems for heat of atomization , so I am confused on how to write the chemical equations for them. Question: The heat of atomization is the heat needed to separated gaseous atoms from a substance in its standard state. The...

Homework Statement Heated iron with mass of 55.0 g was added to 100 mL of water at 20 degree Celsius. Assuming no energy transfer to the surroundings and that the final temperature of the system is 42.7 degrees C, calculate initial temperature of the iron. Mass of Iron = 55.0 g mass of Water =...

Homework Statement I came across this equation ##L / T = \Delta S## and am not too sure about its derivation. From what I know, ##L = Q/m## and ##Q = TdS ##. Substitution gives me ##\Delta S = mL / T## which isn't correct. Could someone assist me in understanding the derivation? Thanks...

Hello When mixing a strong acid and water, the temperature increases. There is production of water molecules from H + and OH- ions. If you plunge a glass of pure water into an intense electric field, the ions present in the pure water will migrate. The pH equilibrium will no longer be...

Homework Statement A standard man climbs 15 m up a vertical rope. How much energy (in cal) is dissipated as heat in a single climb if 23% of the total energy required is used to do the work? (Assume the standard man has a mass of 70 kg.) Homework Equations Q = mgΔh The Attempt at a Solution I...

Hello, I am reviewing some thermodynamics and heat engines. Heat engines are cyclical machines able to convert a portion (just a portion) of the thermal energy extracted from a hot reservoir into mechanical work. The residual thermal energy must dump into a lower temperature reservoir...

Hello. I have an 'Earth and Space Science' topic test tomorrow. Heavily revising, I come across a section that will be in the test: geothermal energy. It works by cold water being pumped down in pipes, underground and then back up, hot, in form of steam to spin turbines and generate...

Homework Statement A 2.56g sample of anthracene, C14H10, was burned to heat an aluminum calorimeter (mass=945 g). The calorimeter contained 1.50 L of water with an initial temperature of 20.5 C and a final temperature of 34.3 C. a) Calculate the molar heat of combustion of anthracene...

I'm involved in a project with central heating. Due to a miscalculation the apartment radiators are about 50% too large. The current system water flow is based on the assumption that the radiators are the correct size (i.e. smaller), even though they are not. Due to this the water takes longer...

Homework Statement The experiment : How the elasticity of material might change under heat treatment? The experiments conducted in two different way, first one the hot bobby pin set to cool down slowly after heated (the professor called annealing treatment), and the second one the pin set to...

I only have a background in mathematics, and I lack knowledge on this matter. I want to get quantitive value about that problem. What would be the kind of wave or EM field that could heat human tissu of 1°C in (say a body part like the thigh), say in one hour, at a distance of 2m ? We could...

Homework Statement Hi all, I came across these steps in my notes, relating to a step whereby, $$\hat{G} (k, t - t') = \int_{-\infty}^{\infty} e^{-ik(x - x')}G(x-x' , t-t')dx$$ and performing the following operation on ##\hat{G}## gives the following expression, $$[\frac{\partial}{\partial t}...

Homework Statement Hello Everyone, We did an experiment using 3 types of heat exchangers this week, double-pipe, shell in tube and plate type. Water was flowing in the HEs, the temperature was set. We had to change the flow-rate only. After the experiment, we were given lots of online...

Homework Statement Question C(ii) Homework Equations dQ/dt =-kA(dθ/dx) dQ/dt = (θ1-θ2)/ ((lx/kxAx)+ (ly/kyAy)) The Attempt at a Solution So the first time I tried at this question, I was using the second equation provided above,but when I check the answer, they put the area on the numerator...

Hi, wondered if anyone can give me a pointer on this problem I am working on. 6 Diesel engines each with power 55kW running, given output cooling water temperature of 80°C, and required return temp of 60°C. The coolant is to be fed through a heat exchanger, with the heat exchanger outlet to be...

Homework Statement Question (b) (iii) Homework EquationsThe Attempt at a Solution The energy required to melt the ice is Q1=mL=3*0.025*3.3*10^5=24750J The energy released by water is Q2=mcT=0.33*4200*(22-T) Shall I calculate the energy that the ice needs after it melts into water? i.e...

I am trying to write code for analytical solution of 1D heat conduction equation in semi-infinite rod. The analytical solution is given by Carslaw and Jaeger 1959 (p305) as $$ h(x,t) = \Delta H .erfc( \frac{x}{2 \sqrt[]{vt} } ) $$ where x is distance, v is diffusivity (material property) and t...

Homework Statement Here is the original question (just read the English version). Homework Equations Q = mcθ Specific heat capacity of water, c = 4200 J/kg °C The Attempt at a Solution I did Q_(absorbed) = Q_(released) mcθ = mcθ mθ = mθ And I solved for the final temperature, which is...

The solution of 1D diffusion equation on a half line (semi infinite) can be found with the help of Fourier Cosine Transform. Equation 3 is the https://ibb.co/ctF8Fw figure is the solution of 1D diffusion equation (eq:1). I want to write a code for this equation in MATLAB/Python but I don't...

Homework Statement Calculate q, w, ∆E, and ∆H for the process in which 93.0 g of nitrous oxide gas (N2O) is cooled from 179°C to 55°C at a constant pressure of 4.00 atm. Cp(N2O) = 38.70 J K-1 mol-1 Homework Equations q= mCΔT ΔH=n(Cp)=n(qv)ΔT ΔE=q+w w= -pΔV *Probably something else too but I'm...

Homework Statement A fuel gas consists of 75% butane (C4H10), 10% propane (C3H8) and 15% butene (C4H8) by volume.It is to be fed to the combustion chamber in 10% excess air at 25oC, where it is completely burnt to carbon dioxide and water. The flue gases produced are to be used to generate 5...

Hello, After the last post I completely changed the system. I now have a new system. Based on the feedback from last time I increased the time in contact with the block significantly. And I have made it a two stage unit. Here are the parameters for the first stage. An Aluminum block. (assume...

Homework Statement Find the expression for c_p - c_v for a van-der-waals gas, with the equation of state \Bigg{(}p+\dfrac{a}{V^2}\Bigg{)}(V-b)=RT Homework EquationsThe Attempt at a Solution Basically I've proved c_p - c_v = \Bigg{[} p + \Bigg{(}\dfrac{\partial E}{\partial V}\Bigg{)}_T...

Capillary action is a form of work, i.e. an object (water) moved by a force (capillary action) over a distance. Since all work requires energy, what supplies the energy for capillary action? Is the chemical energy of the water increased by adhering to a surface? Perhaps the heat energy of the...

Homework Statement There is a picture attached showing the entire problem. Equation 2.78 is the Clausius Clapeyron equation. Homework Equations Clausius Clayperon equation. L = L'T (since there is a linear dependence on temperature) The Attempt at a Solution $$ \frac{de_s}{dT} =...

Homework Statement [/B] Phospine exist in three forms. known as the \alpha, \beta and \gamma forms. The \alpha and \beta forms are in equilibrium with each other at 49.43 \, K, and the \alpha and \gamma forms are in equilibrium at 30.29 \, K. Obtain the molar heat of transformation for the...

since specific heat c changes with temperature, but its treated as a constant in the heat formula, so that means that heat formula Q=mc(T2-T1) is just an approximation? correct? I see some texts define heat as Heat, q, is thermal energy transferred from a hotter system to a cooler system that...

Homework Statement I have the heat equation $$u_t=u_{xx}$$ $$u(0,t)=0$$ $$u(1,t) = \cos(\omega t)$$ $$u(x,0)=f(x)$$ Find the stable state solution. The Attempt at a Solution I used a transformation to complex to solve this problem, and then I can just take the real part to the complex...

Homework Statement I need to find the time it takes to heat a vessel of water which is closed. Here is what I have: Specific heat capacity of water: 4184 J kg^-1 K^-1 Density of water: 1000 kg m^-3 Volume of water added and volume of vessel: 500 L or 0.5 m^3 Heat capacity of the vessel: 91000...

Homework Statement A great deal of effort has been expended to find “high temperature superconductors”: materials that are superconductors at temperatures higher than the boiling point of liquid nitrogen (77 K). Most of the older superconductors had to be operated with liquid helium (boiling...

I'm a bit confused as to how to imagine a negative sensible heat flux near the Earth's surface. Negative means that sensible heat is moving towards the surface. My book states that that would mainly occur at nighttime. During day there is a positive sensible heat flux and sensible heat moves...

But not for the reason or application you might think...lol I live in SE Texas, just south of Houston. It is hot as balls here in the summer. (Which accounts for three of our seasons here) My neighborhood is on a "community well" type water system, and the well is in the back of the...

I would really like a logical explanation for some of the factors that affect convective heat transfer coefficient. I have only found mathematical one. For example: 1) Properties of the fluid: 1)Velocity: My professor said that the lower the velocity the more time the fluid gets to interact...

Homework Statement A short metal cylinder 145 mm in diameter and 145 mm high at 1045 K is suddenly exposed (all sides exposed) to a room air temperature at 300 K with h=25 W/m².K. Assume that for the metal k=40W/m.K, den=7800 kg/m3 and Cp=c=600 J/kg.K. Estimate (a) the time required for the...

<mod: moved from intro> Hello all! This is my first post in this forum. I am struggling with the following question regarding a hair dryer. The hairdryer can be seen as a cilinder with a fan inside blowing air at speeds from the table below and 1 nichrome wire which heats up consuming different...