Heat Definition and 1000 Threads

Homework Statement Wet clothing at 0°C is hung out to dry when the air temperature is 0°C and there is a dry wind blowing. After some time, it is found that some of the water has evaporated and the remainder has frozen. Estimate the fraction of the water originally present in the clothing which...

If I have a tank half-filled with low boiling point liquid at ambient temperature, then this tank is placed inside dry oven whose temperature is kept to be around 5℃ above the liquid boiling temperature. A fan is placed inside the dry oven as an effort to make temperature distribution even or at...

Homework Statement Calculate the power needed to heat a 1360 gram chunk of ice in a 600 gram copper pan from 0 ◦C to the system’s final temperature of 35◦C in a time of 10 minutes. Homework Equations Q=mcchange in temp Q=mLf P= energy/time The Attempt at a Solution I thought that adding the...

If I heat up an object,the object emits a electromagnetic wave with a shorter and shorter wavelength. But if I heat an object up to Planck temperature, and making the EM wave that it emits has a wavelength of Planck distance,what will happen when I heat it up even more? Will the wavelength...

Homework Statement Please look at the screenshot. Homework Equations dimensional analysis The Attempt at a Solution Since the heat capacity is given as 11.3 kJ/(C*g), and energy is measured in Joules (or kJ), I thought to multiply 11.3 by the change in temp (7.3 C) and also 1.50 g of...

Homework Statement The combustion of toluene has a ΔErxn of −3.91 × 103kJ/mol. When 1.70 g of toluene (C7H8) undergoes combustion in a bomb calorimeter, the temperature rises from 23.36 ∘C to 36.67 ∘C. Find the heat capacity of the bomb calorimeter to three sig-figs. Homework Equations q =...

I am doing an assignment about heat energy transfer and passive cooling. I understand that heat energy is transferred into rooms through windows by conduction, but I'm confused about if heat energy is also transferred through windows by solar radiation and where infrared radiation comes into...

Supposed you have a box of size 1 square foot and the insulation is 100% efficient.. meaning there is no transfer of any heat outside.. and you put a lamp with glass surface temperature of say 50 Celsius (155 Fahrenheit). Would the air temperature in the box keep increasing... can it reach 1000...

Homework Statement In a certain process, a gas absorbs Q amount of heat and performs kQ amount of work, the molar heat capacity of the gas in terms of R, k and γ(Cp/Cv) is? Homework Equations U=Q+W U=nCvdT Q=CdT The Attempt at a Solution replacing U and Q with the above formulas and W from...

Homework Statement A piece of metal is heated by supplying a constant power P. The temperature of the metal starts varying as T=kt. The heat capacity of the metal as a function of temperature is? Homework Equations Q=CdT The Attempt at a Solution From Q=CdT, dT is k, since P is Q/t, I plugged...

Homework Statement A metal block of mass 10 kg is dragged on a rough horizontal surface with a constant speed of 5 m/s. If the coefficient of kinetic friction between the block and the road is 0.4, then the rate of generation of heat is. take g=10 m/s^2? Homework Equations F=ma Frictional...

Hi all. First, some context. I work for a small seed oil extraction plant where we cold press the seed then solvent extract the residual oil from the presscake. In the solvent extraction plant we use liquid ring pumps to pull the required vacuums. The Plant Vac Pump (PVP) is used in all...

Homework Statement Consider the dissolution of CaCl2. CaCl2(s) Ca2+(aq) + 2 Cl-(aq) ΔH = -81.5 kJ A 10.6-g sample of CaCl2 is dissolved in 109 g of water, with both substances at 25.0°C. Calculate the final temperature of the solution assuming no heat lost to the surroundings and assuming...

Why specific heat of solids and liquids doesn't change with change in temperature?

Hi guys, I am currently working through a book about thermodynamics and statistical mechanics as I was not so great in these course during my undergrad studies. First question: The book introduces heat as the kind of energy that terminates the temperature of a system. In other words: Give heat...

Hi, I have been trying to set up a funtcion of the temperature over time and I am doubting my results. In the system i have: Fig 1. The system is at rest. For simplicty I've considerd the ambient temperature to be same as T1. By knowing: Fig 2. yeilds: Fig 3. In my case B&C is at a...

Hi, I wanted to do some rough "back of the envelope"-calculations of heat losses from pipes, with water circulating in them, to compare to the results of various programs' simulations. I was not very successful as I was perhaps hoping to get rough estimates in the range 20-200% off, but right...

Hello! (Wave) Let $\phi \in C^1(\mathbb{R})$ and periodic. We consider the problem $u_t=u_{xx}, x \in \mathbb{R}, \ 0<t<\infty$, with initial data $\phi$. I want to compute a formula for a solution $u$ and I want to prove strictly that this formula solves the initial value problem. I also...

My book states that Heat and work represent energy in transit. The state of the system undergoes a change after heat is supplied to it and before work is extracted from it because energy gets stored in it. My doubt is here that ,heat has been transferred to the system and it says heat is energy...

Carlo Rovelli described in "The Order of Time" that "Living beings are made up of similarly intertwined processes. Photosynthesis deposits low entropy from the sun into plants. Animals feed on low entropy by eating. (If all we needed was energy rather than entropy, we would head for the heat of...

Homework Statement Prove the following relation for which clausius equation holds : Cs=Cp-αV(ΔH/ΔV) Where Cs=∂q/∂T at constant S and is the heat capacity in the coexistence line of 2 phases Homework Equations dq=dU+dW dP/dT=ΔH/(ΔV*T) The Attempt at a Solution I do not fully understand why q...

If I was attempting to calculate the amount of energy transferred as heat to an object free-falling in the atmosphere, is this how I could go about it?... Work = (Drag Force) x (Displacement through atmosphere) = Energy transferred as Heat I am attempting to solve a hypothetical question...

Homework Statement (c) A heat exchanger is to be used to heat a process liquid within the tubes using saturated steam at 100oC. The tubes have an inside diameter of 20 mm and outside diameter of 22 mm. It is estimated that the inner surface heat transfer coefficient will be 4.2 kW m-2 K-1 and...

Homework Statement [/B] Hi guys. Been looking at this question for a while and can't figure it out. An aluminium furnace is fuelled with propane gas. The furnace is loaded up with 4 aluminium ingots each of mass 22.5 kg. The question is: If 2.1 kg of propane is used to complete the melting...

If I have a box evacuated of air with 5 of the sides mirors and one side a heat conductor. will the photon gas inside have photons that get absorbed by the heat conductor and re-emitted when the photons strike the heat conductor

What information / formulas do I need to calculate / estimate the amount of time required to melt an ice cube of temperature $T_i$ and mass $m$ in $M$ kg of $T_w$ temperature water? Assume that the system is insulated. Is it even possible? I'm fine with Calculus.

We have a glass containing 0.5 liter (0.5 kg) of water whose temperature 100 degrees Celsius. We also have an ice cube with mass 0.01 kg and temperature -10 degrees Celsius. The cube is put into the glass. The glass is then insulated from the outside world, until the cube has melted. What will...

Recently looked at why temperature flows from high Temperatures to Low temperatures.Essentially it was laid on two Fundamental Assumptions: 1.Energy is conserved in the isolated system 2.Entropy in isolated non quasi static systems will always tend to increase. Lets take a brief look at...

Hi there, Hopefully this is a very easy question and you all can just confirm this for me. When calculating heat transfer into a fluid from a heated tube, is it correct to say that the heat transfer coefficient is *not* dependent on the tube diameter? So, if we solve for T_{out}, we get...

Homework Statement In a reversed heat engine, the work done on the engine is 85 kJ and the heat transfer to the engine from the low temperature region is 260 kJ. Determine: 1. the heat transfer to the high temperature region 2. the coefficient of performance as a refrigerator Homework...

Hello, I am writing a blog article about storing solar energy as heat. Can someone credible check this? I calculated I need 185.4 liters of vegetable oil to substitute a 6.4kWh battery if I had the same energy conversion (Tesla says 90%) and energy loss over time (no idea about this value) as...

Hey there! I want to make a rosin press from scratch. I have a big press with 2 inch thick metal plates, probably about 4 inches wide and 10 inches long. I need to heat these plates up to 230 degrees Fahrenheit and press them against each other with product in between them. I am going to fasten...

Phonons on their own lead to the common heat equation. One sees that for example in insulators or non doped semiconductors. However in metals (or conductors), the electrons are the ones that are mostly responsible for the heat transfer, which extremely surprisingly to me, is also of the form of...

Hi! Basically I have some tasks in thermodynamics calculating the heat transfer through a wall. I have been attempting to solve the following problem: “Calculate the heat transfer through the exterior wall in a building, where the temperature inside the building is 20 °C and the temperature...

So say I've got a wheel who's outer radius is 12" and the radius of the axle is 1.5", so the simple machine here is an 8 to 1 ratio. So I am wondering, since 1/2mv^2 is for kinetic energy, and the velocity here is 1/8th, does it mean the friction is 1/8th or 1/64th? does it get 1/8th hotter or...

In bolometers, incoming radiation warms a strip of material. this material will have a large thermal coefficient of resistance, leading to a (small) resistance change in the material. the inventor, Samuel Pierpoint Langley apparently used this to detect a cow from 1/4 of a mile away using a...

So enthalpy is the heat content of a system at constant pressure. Enthalpy change is equal to the heat absorbed or evolved by the system at constant pressure. If my understanding is correct, a system whose temperature goes up will return back to that starting temperature if pressure is kept...

Consider two solid objects in the vacuum (of different materials, if you will) at different temperatures approaching each other until they make "perfect contact" through flat surfaces (no gaps or defects, so that thermal contact conductance effects are absent, even though interfacial thermal...

Hi everyone I'm new around here and I wonder if anyone can help please. I'm taking hot air off the chimney stack inside a factory at a temperature ranging between 700 and 400 degrees going through a 4 inch stainless steel pipe with 3mm wall thickness. This pipe line will be about 35 meters long...

Homework Statement A researcher studies the heat transference between an iron block and an unknown substance, inside an adiabatic calorimeter. In successive experiences he puts inside the calorimeter the unknown substance, always in its solid state and with temperature θs = 20ºC, and the iron...

I wish to numerically compute solutions of the 1D heat equation using the Crank-Nicholson scheme: The equation is: \partial_{t}u=\partial^{2}_{x}u I use the discretisation: u_{i+1,j}-u_{i,j}=s(u_{i+1,j+1}-2u_{i+1,j}+u_{i+1,j-1})+s(u_{i+1,j+1}-2u_{i+1,j}+u_{i+1,j-1}) Where s=\delta...

If this is a valid enough definition of a heat engine: All heat engines transfer heat energy from higher to lower temperatures, and do work in the process. ... then is the human body a heat engine?

Homework Statement How much heat in joules must be added to 0.841 kg of aluminum to change it from a solid at 130 °C to a liquid at 660 °C (its melting point)? The latent heat of fusion for aluminum is 4.0 x 105 J/kg. Homework Equations Q = mL Total = mc∆t + mL = m(c∆t +l) The Attempt at a...

I recently read in a Khan Academy article that the rate of energy exchange through heat across a material of thickness ##d##, surface area ##A##, and thermal conductivity ##k## can be approximated by $$\dot{Q} = \frac{kA\Delta T}{d}$$ where ##\dot{Q}## is the heat rate and ##\Delta T## the...

Homework Statement Homework EquationsThe Attempt at a Solution No . The number of photons should decrease . As the rate of heat transfer decreases with time , the net electromagnetic radiation from the hot body to the surroundings decrease . Heat radiations are composed of photons ...

Yes compressing air increase its temperature but does that necessarily increase pressure? In an pellet gun a spring driven piston compresses the air which increases the temperature but wouldn't any increasing pressure simply retard the piston's advance? Because the chamber volume is not fixed...

Homework Statement Hello. First of all sorry about this question, it has to do a little with heat transfer from engineering. This situation is not real, I was working in a proyect and this doubt came to me. I have a heat exchanger of parallel tubes. Water flows in a tube and oil flows in...

There's a passage in Kumar's (excellent) book, "Quantum", which has me confused. He notes that Planck is aware that as the temperature of a heated poker rises, the colours change from red through to bluish white. Later in the passage, he refers to Herschel's earlier work on the relationship...

I have seen how to solve the heat equation: $$ \frac{ \partial^2 u(x,t) }{\partial x^2} = k^2 \frac{ \partial u(x,t) }{\partial t} $$ With boundary conditions. I use separation variables to find the result, but i don't know how to solve the equation plus a...

Homework Statement Find the admissible current density Jadm for a wire that has no insulation and also for a wire that has two layers of insulation and compare it to Jadm for the case when the wire has only one layer of insulation.2. The attempt at a solution and equations In the image I've...