Heat Definition and 1000 Threads

When calculating heat transfer, how would one know when to use Q=T*m*(delta s) versus Q=m*(delta h). I'm confused when we should calculate using entropy versus enthalpy. Anything helps. Thank you!

Homework Statement In order to stay warm, divers often wear some sort of thermal protection, like a "wetsuit". Often this is a neoprene "foamed" material, which traps gas bubbles as the insulating material. For this problem, assume: the thermal conductivity is that of air (κ = 0.03 W/m-K) the...

Hello, I am trying to achieve a range of temperature (below 0 degC) by heating up liquid nitrogen (77K) with an electric heater (100W) inserted into a copper block. How do I calculate the time taken (t) for the nitrogen vapour to reach temperature T (say 100K). The liquid nitrogen is poured into...

How would one calculate the heat generated by a rotating body inserted into a different softer material? Similar to a drill bit, but without the cutting edges so a smooth constant profile across the probe surface.

Homework Statement Hi, I have an assignment to determine the specific heat capacity of water using a calorimeter, voltmeter and ammeter, where we connected the calorimeter to a 10V power pack and measured the temp of the water and the readings on the voltmeter and ammeter every minute. I ended...

I am not a mechanical engineer; but I have physics background. I want to lift about 250 watts of heat from a metal block. At the same time I have to maintain its temperature at 30 deg Cel. For this I want to use water-air heat exchanger (HE). Heat exchanger will have inlet & outlet pipes. Hot...

Homework Statement Im working on the following problem and could need some help in answering them: Work is being produced from a cycle. In order to produce this work, energy is being taking from a high temperature sources at a ratio of 1000 kJ/kg and the extra energy is being deliver to a...

In running my vacuum cleaner, I have noticed that the plug end of the cord gets warmer than the rest of the cord. Since the wire gauge and current must be the same through the entire length, why would this happen? I have noticed this regardless of the wall socket that I use and it doesn't seem...

Homework Statement A 75.0g ice cube at 0 C is placed in 825g of water at 25 C. Find final temp. Homework Equations Well none really, this should be simple plugging into to heat equations. The Attempt at a Solution Heat required to melt ice = (0.075kg)(3.33*10^5) = 24975 J Heat required to...

First of all, even I did mentioned Solar Cooker, the main goal is to reach most temperature of 500ml of water in 30 minutes. Basic information that I have is some material with different thermal conductivity. I seek for simple english language and a bit complex physics language. The idea of...

Homework Statement The mass of liquid nitrogen in an open beaker is found to have decreased by 46.3 g in 10 minutes. If the s.l.h of vaporisation of nitrogen at its boiling point is 1.99 x 105, at what rate were the surroundings heating the beaker? Why is the heat capacity of the beaker...

I have a heat source in the form of a waste oil heater for a small workshop, i get around 200 degrees C from it and it warms the workshop up nicely. What i am wondering is is there a way i could produce enough electricty to run a small water pump from the excess heat? Something like a 12v pump...

Homework Statement Kindly refer to part (c). The woking should be power/0.35 (what I think according to the graph). But the answer is power (that is the answer of part b) divided by 0.02 Homework Equations I have used the ratio method simply The Attempt at a Solution According to part (b)...

I was wondering how a boundary layer would be dissipative of momentum if it was under the influence of a positive heat gradient. I understand that the reason that we don't see the boundary pressure equal the stagnation pressure is that the boundary is dissipative (so excess pressure above...

I’m working on an experiment and would appreciate some guidance to characterize the performance of it. I have a small homemade copper coil submerged in a 3 gallon water tank. I’m delivering hot water to the coil that in turn heats the water in the tank. I sense I’m looking for a rate of heat...

So i did a lab were we melt an ice cube in water. So i have to find the heat of fusion for the ice cube. But i am not sure how to do that. What i was thinking of doing is finding the energy released by temperature of the ice cube increasing, then make that value of q, equal to m*hf, when it is...

Homework Statement A metal block of heat capacity 60 J K -1 loses 1MJ of heat energy to its surroundings. Find the decrease in its temperature. Homework Equations Q = m c Δ θ Heat energy added = mass x specific heat capacity x rise in temperature heat energy lost = blah blah blah x drop in...

Homework Statement A 1x106 kg piece of ice is placed into a lake. How much heat is taken from the lake to raise the temperature of the ice from 0 °C to 1x10-20 °C? How much volume does the lake increase by? Latent heat for water is 334x103 J/kg Homework Equations Found in my textbook, cice =...

I don't understand what is heat actually. And what are the physical constituents that make up this entity.

Homework Statement I do not need to solve this problem, see below. EXAMPLE 7.1 Air at a pressure of 6kN/m2 and a temperature of 300C flows with a velocity of 10m/s over a flat plate 0.5m long. Estimate the cooling rate per unit width of the plate needed to maintain it at a surface temperature of...

why wave with lower frequency produce heat? please explain to me

I was doing a science experiment involving enzymes and hydrogen peroxide, and by adding heat to the catalase, it should have sped up the reaction, but instead it slowed it down. Is there a reason why this happened?? Isn't heat supposed to speed up the reaction, instead of slowing it?

Homework Statement Homework Equations Heat equation The Attempt at a Solution I can derive E(t) to get integral of du/dt over 0 to L, which is the same as integrating the right hand side of the original equation (d2u/dx2+sin(5t); while this allows me to take care of the d2u/dx2, I don't know...

Homework Statement n = 3.8-mol of diatomic gas is allowed to expand isothermally from Vini = 1.9-m3 to Vfin = 10.5-m3. The initial pressure is Pini = 1.38-atm. After this the gas is raised at a constant volume by a temperature ΔT = 35-K. Calculate the total heat flow into the gas. Homework...

I have not much experience in solving pde before except using the separation of variables. I am trying to solve the following equation where omega is a box. Is there a close form of the solution? How should I approach the problem? Much thanks!

Homework Statement A spherical shell has inner and outer radii r_a and r_b, respectively, and the temperatures at the inner and outer surfaces are T_a and T_b. The thermal conductivity of he shell material is k. Derive an equation for the total heat current thought the shell in the steady...

Hi everybody! I was wondering, what substances do form when plastic is heated? I found on the internet that if plastic is heated in the oven (not microwave) at 325°C, it shrinks and become more thick, and it can be used for art work. I tried to search about it, but I found different opinions...

Homework Statement a copper pot's radius is 12 cm, the thickness is 5 mm. It is placed on the stove for boiling, if the temperature of the stove is 115 oC while the water is 100 oC. How much of water that evaporates per minute Homework Equations ΔQ/Δt = (A)(k)(ΔT) / (L) Q=mcΔT The Attempt...

HOMEWORK POSTED IN WRONG FORUM, SO NO TEMPLATE I have encountered a problem at the university in which there is a thermally isolated container of constant volume in which the number of particles and temperature change with time(the temperature increases). The change in particle number ensures...

I am building a Rapid Pulse Carbonation prototype Reactor unit, I am capturing the Steam form the process and passing it though a Plate and Tube condenser to produce water, also I will capture the CO2 gas from the heating system. How would I reduce the exhaust gas heat before I pass the exhaust...

There's one equation that I've seen being used already, which by itself is quite simple, but I can't understand where it comes from. The context is as follows: suppose we have one heat engine operating between systems A and B whose temperatures are T_A>T_B. Let's suppose further that the...

I was watching a video in which they said that HSP is produced to help proteins fold correctly and to prevent them from tangling up and misfolding. But, if the cell is producing another protein, wouldn't the chances of tangling up and misfolding increase (because now you have one extra protein...

I need to cool a slow moving small flow of hydroponic plant water, at most 1000 ppm nutrients, with a pH of typically around 6. I'd like to use aluminum or copper heat sink directly in that fluid stream to drop temp 10 or 20 degrees F down to 50-60F neighborhood. My concern is I don't want...

A gas in a cylinder with constant pressure, the gas cooled down and its internal energy decreased as well as its volume. The heat Q will be flowing into the gas or out of the gas? My try for the solution: As the volume decrease the work done by the gas will be negative. The gas cooled down, so...

Technically, this isn't a question concerning supercritical fluids. It's more about converting thermal energy into velocity by playing "keep-away" with molecules that want to go supercritical. The idea is simple. In an fully contained system, we can more or less say volume is static...

Hi, layman here. As I understand, the theoretical Heat Death of the universe would imply that the accelerating space expansion reaches an expansion rate so big that it takes bodies and eventually even fundamental particles apart, leaving them alone up to an ultimate point in which no particle...

Hi, I am looking for the reasons for the generation of heat developed in a material due to electron bombardment. Searching in the internet gives me only the estimations of the heat developed, but not the physical reasons for the heat development. Appreciate if I am provided any insight into the...

Homework Statement Homework EquationsHEAT PRODUCED=WORK DONE BY BATTERIES - ENERGY ABSORBED BY CAPACITORS The Attempt at a Solution INITIALLY BEFORE SWITCH CLOSED :Initially a current flows only in the left most loop involving 4 microfarad capacitor.The charged on the capacitor during...

My longtime friend moved recently and his new place has an in-ground pool. He's a bit* of an Engineering nerd he has decided to build a solar heater from scratch. Him being a neophyte at the art of pool science though, I felt it my duty - despite being someone who never got his own custom...

This is an experiment I have wanted to do for a few years now but don't have the necessary equipment. GR tells us if you have identical objects with the same weight exactly when they are at the same temperature, then when one object is heated, it will weigh more. This is because the...

A HUGE topic of conversation on many car forums, I thought I would bring it here. Many cars have chrome tin in the engine compartments to make them look flashy. However, for decades now, people say the chrome reflects the heat back onto the engine block and to paint the engine compartment black...

Homework Statement I would really appreciate if you could give me some hints regarding what exactly to do at iv)[/B] iv) Given formulas: Homework Equations f(y)=(ro*R^5/E*t^2) The Attempt at a Solution we know that f(y)=0.75 1ton TNT=4.184*10^9 J ro=1.003kg/m^3 We have the above...

Homework Statement so, i had this question where i had a sphere and a cylinder with given dimensions and propreties ( roh, C and k) he also gave me initial temperatures, then both of them dipped in a bath of water of given temperature but unknown h ( convective coefficient) then he gave me the...

Homework Statement Homework Equations The Attempt at a Solution I do not know exactly how to start this problem. I would really appreciate it if you could give me some hints. I know that e^ - t/tau=T(t)-Twall/Ti-Twall where tau=m*cp/hA where h=convective heat tr.coeff and T(t) is desired temp...

Hi Guys While studying physics for my masters (doing it in material science engineering), huge amount of questions appeared. First, let's imagine two experiments 1) One enclosure with perfect reflective walls (R=1 over the entire thermal radiation spectra) at a temperature T1 and a body inside...

Homework Statement State and use simple assumptions to show that ' Power is proportional to V^5' is the expected relationship for a pure tungsten filament bulb. Homework Equations V=IR I=dq/dt Q=mcT The Attempt at a Solution I tried to use a simple model where the rate of heat loss is...

Hey all, first time posting! So I'm having trouble with understanding the differences between the constant heat flux and constant temperature condition when not in a textbook. Some research I have begun working on involves a strip of heat tape sandwiched between two aluminum plates which are...

Hello, i am new at the forum and i hope i can help and get helped so we can move forward in our projects/jobs/studies. I also ask please to correct any gramatical or vocabulary mistake, since i am still learning english. Now to the actual problem. I am already building some kind of epoxy resin...

Homework Statement Using equipartition law, find specific heat of gas containing triatomic linear molecules. Will the result be different if the molecule was non- linear? In what way? Homework Equations According to equipartion theorem, each degree of freedom gets (1/2)kT kinetic energy and...

I have uploaded a page from my prof's lecture on specific heat. Its given that average energy for each vibrational mode is $$\frac{h\nu}{e^{\frac{h\nu}{T}}-1}$$ Hence $$U=(\text{number of vibrational modes)}\times\frac{h\nu}{e^{\frac{h\nu}{T}}-1}$$ In the lecture slide, the number of...