In thermodynamics, heat is energy in transfer to or from a thermodynamic system, by mechanisms other than thermodynamic work or transfer of matter. The various mechanisms of energy transfer that define heat are stated in the next section of this article.
Like thermodynamic work, heat transfer is a process involving more than one system, not a property of any one system. In thermodynamics, energy transferred as heat contributes to change in the system's cardinal energy variable of state, for example its internal energy, or for example its enthalpy. This is to be distinguished from the ordinary language conception of heat as a property of an isolated system.
The quantity of energy transferred as heat in a process is the amount of transferred energy excluding any thermodynamic work that was done and any energy contained in matter transferred. For the precise definition of heat, it is necessary that it occur by a path that does not include transfer of matter.Though not immediately by the definition, but in special kinds of process, quantity of energy transferred as heat can be measured by its effect on the states of interacting bodies. For example, respectively in special circumstances, heat transfer can be measured by the amount of ice melted, or by change in temperature of a body in the surroundings of the system. Such methods are called calorimetry.
The conventional symbol used to represent the amount of heat transferred in a thermodynamic process is Q. As an amount of energy (being transferred), the SI unit of heat is the joule (J).
Hello everyone,
For villages in Africa and Asia that still use wood, dung or other biomass in simple stoves which option do you think will be better?
Concentrate solar energy into an insulated unit with a molten salt which can then be used at any time or build a simple biogas generator (large...
Homework Statement
After a free expansion to quadruple its volume, a mole of ideal diatomic gas is compressed back to its original volume isobarically and then cooled down to its original temperature. What is the minimum heat removed from the gas in the final step to restoring its state...
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I'm aiming to produce a lightweight steam engine, which will essentially have a coil of copper tube inside the walls of a tube made of >your suggestions here<. this tube is the exhaust for a blowtorch.
The principle is that this tube gets very hot, then transfers heat to the...
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I have small question , as I read about the ATF research in the news ,a question present it self , why no one does any research on heat carrier in nuclear reactor that can absorb nuclear radiation and change it to infra red radiation ?
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H
I'm trying to get a better handle on the actual physical phenomena underlying viscosity (for Newtonian fluids). Something I could word in the format of "this happens (and this and this), and so the fluid resists flow." What I've found online is that when gasses are at higher temperatures, they...
Homework Statement
For the reaction below, the constant pressure heat of reaction is qp = −3256 kJ mol−1 at 25 °C. What is the constant volume heat of reaction, qV , at 25 °C?
16 CO(g) + 33 H2(g) ⟶ C16H34(l) + 16 H2O(l)
Enter your answer in kJ mol−1, rounded to the nearest kilojoule...
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I've got a Heat Transfer problem that I can't seem to get right.
I will list all information in the problem without 'interpreting' it:
Givens: 100 cm long cylinder filled with hot water, and constantly heated to maintain the water at 100°C. Heat is transferred via conduction from...
Homework Statement
An insulated beaker with negligible mass contains a mass of 0.350 kg of water at a temperature of 76.5 °C.
How many kilograms of ice at a temperature of − 23.9 ∘C must be dropped in the water to make the final temperature of the system 40.0 ∘C?
Take the specific heat for...
hello my friends ,
i have two question about calorific value of coal
why Lower heating value decrease with increase oxygen content but increase with increasing hydrogen , sulfur and carbon content ? Do this elements influence the higher heating value or not ?
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Homework Statement
How many kilograms of lpg will you use if you heat 5 litres of water from 20C to 90C everyday for 30 days and how much will that cost if a 12.5kg cylinder is 1750 Rupees
The attempt at a solution
To heat 1 liter of water by 1C requires 4.18kJ so you then...
Hi all, I have encountered the idea of a heat bath but am slightly perplexed as to what it is.
There was a textbook example that looked to find the number density expression for gas molecules as a function of position (image below). It then said that the probability ##P(z)## of finding the...
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I suffer from having a very cold house - as it is rented, we cannot put insulation in or change the windows (single glazed!), so I am looking for non-permanent options to maximise the warmth we can get from it.
We have a log burner, and I have found that it is still kicking heat out...
Homework Statement
A circular metal plate of diameter D needs Q Joule of heat to expand and the temperature changes from 40oC to 58oC. What is the thermal energy needed to expand identical metal plate having twice the diameter for same increase in temperature?
Homework Equations
Q = mcΔT
The...
Can anyone point to a refereed paper exploring the heat absorbed by melting around 500 GT of ie per year (Antarctic - 127 GT pa; Greenland 286 GT pa; sea ice, glaciers estim. 100 GT pa)?
As latent heat of fusion is 333.55 KJoules per Kg, I reckon the heat absorbed per year is around 1.67 X 1023...
Homework Statement
An inventor claims to have developed a device with the following properties:
net work output per cycle = 20,000 J
heat output per cycle = 50,000 J
high temperature = 450 C
low temperature = 160 C
Calculate the heat input per cycle.
Homework Equations
ΔETH = W + Q
efficiency...
I have recently been curious about heat diffusion. If there is space in one dimension with any kind of temperature dispersed throughout, then the heat equation states that the derivative of the temperature with respect to time at any point equals some constant (k) multiplied by the second...
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the efficiency ##\eta## of a generic heat engine working between two temperatures is bound from above by the efficiency ##\eta_{\rm C}## of a Carnot machine working between the same temperatures.
That is, if the temperatures are the same, a (ideal) Carnot machine is better than any...
1. In studies of the heat budget of the global free atmosphere, the concept of “latent heat” (now known as “enthalpy of condensation”) plays an important role[1].
2. Both observation and experiment confirm that when humid air condenses the temperature of the remaining air increases[2].
3. This...
I noticed that the outdoor fan on my residential, split-system heat pump stopped working in mid-October. I don't know for sure exactly when my outdoor fan on my heat pump stopped working. It might be that my outdoor fan did not work for months before I noticed that the outdoor fan did not work...
The outdoor fan on heat pumps always runs when the compressor is pumping refrigerant when the heat pump is in heating mode unless the heat pump has defect(s). I don't understand why the outdoor fan on a split system heat pump needs to run when the heat pump is in heating mode.
When a split...
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My question is: I understand that at noon-day it’s hotter because of the angle with which sun rays enter our atmosphere. But at the same time, I was wondering that the band of radiation responsible for heating things is infrared, and that at noon basically all bands of lower frequency than...
I read some Yogi can sleep naked at snow. Is there any scientific studies how they did it? Also what exactly regulate our body temperature? How much is the role of ATP in it?
1. Homework Statement
The chemical reaction is given:
2C2H2 + 5O2 -> 4CO2 + 2 H2O. ΔrH* = -1299 kJ / mol.
How much heat is released when 50 grams of C2H2 is burned?
Homework EquationsThe Attempt at a Solution
First, I convert mass into moles.
M(C2H2) = 2*12+2 = 26 g/mol
n(C2H2) = m/M = 50 g...
We all know how a thermostat works 2 different type of metal are attach together, when temperature changes 1 metal strap expands more than the other strap causing the straight metal strap to bend.
45 years ago when I was in college the professor brought a desk top heat engine to class. He...
Can liquid helium is superfluidity state conduct heat infinitely fast?
I thought I have seen this is a paper somewhere a long time ago, but now I am not sure about that.
Homework Statement
Keeping the cabaret door closed is important, so you install a sophisticated door control system that keeps the air exchange between inside and outside to a minimum. Why will such air exchanges always require the climate control system to work harder and consume extra...
Homework Statement
Instead of pumping heat into the cabaret air from the outside air, you could simply put an electric space heater inside the cabaret. A space heater turns electrical energy directly into thermal energy. Why would operating a space heater consume more electric power than...
Homework Statement
It is desired to heat 5130 kg/hr of cold benzene from 80 to 120℉ using hot toluene using double pipe heat exchanger. Toluene will be cooled from 160 to 100℉. The specific gravities at 68℉ are 0.88 and 0.87 respectively. A fouling factor of 0.001 should be provided for each...
Homework Statement
Im confused about this and need help
We did heat of nuetralization lab where we reacted 25mL of HCL and 25mL of NaOH using calorimeter.
The temp difference was an increase of exactly 7degC
One question asks me to show q_water (J) and to assume 50g water for the calculation...
Homework Statement
Calculate the amount of heat emitted when 12.4 g of water freezes to solid air.
Homework Equations
heat of fusion = 6.02 KJ
1 mol H2O = 18.02 g H2O
The Attempt at a Solution
12.4 g H2O x 1 mol H2O/ 18.02 g H2O x (-6.02 KJ) / 1 mol H2O = - 4.14 kJ
I am unsure whether the...
Homework Statement
I have delta H _solution, and also the mass of the solitd and q_water and q_reaction.
Im using Dulong Petit to get MM but I need specific heat of the solid obviously.
I don't have a final temp of the unknown solid, just the delta T for the water
thanks for any help
Homework...
My understanding of heat is the energy transferred as a result of temperature imbalance between systems.
If two systems at different temperatures are in contact with each other, a temperature change for both systems and an energy transfer Q is occurring.
It is known that Q=W for a closed...
The ans comes out (c) if I take specific heat at constt volume to be independent of temp.
Whether the specific heat is always temp. independent for an ideal gas??
Homework Statement
One of the two glass panes in each window is coated with a transparent electrical conductor. Why does this coating improve the window's insulating ability?
Select one:
a. The transparent conductor is black in the infrared, with a low-temperature emissivity of almost 1.
b...
The following red highlight is quoted from a website
"
5. PP: polypropylene.
PP is used to make yogurt containers, deli food containers and winter clothing insulation. PP actually has a high heat tolerance and as such, does not seem to leach many of the chemicals other plastics do."
However...
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...
Homework Statement
A cylinder is well-insulated at the base and sides (radially). No heat sources and assume steady state. All other BCs are free (I'm aware the problem is underconstrained). Then we have
$$\nabla^2 f = 0\\
\partial_rf(r=R_0) = \partial_rf(r=R_1) = 0\\
\partial_z f(z=0) = 0\\...