Heat Definition and 1000 Threads

Homework Statement 117 J of energy is supplied as heat to 2.00 moles of an ideal gas at constant pressure, the temperature rises by 2.00 K. Calculate the molar heat capacity at constant pressure C_p,m and the molar heat capacity at constant volume C_v,m for the gas. Is the gas monatomic or...

Question: A pipe of outside diameter 200 mm is lagged with an insulating material of thermal conductivity 0.06 W m–1 K–1 and thickness 75 mm. The pipe carries a process fluid at a temperature of 300 °C and the average temperature of the outer surface of the lagging is 45 °C. (a) Estimate the...

1. The problem What is the resultant temperature when 100g of steam at 100°C is passed through 500g of ice at -20°C.Homework Equations Q=mCDeltaT[/B] The Attempt at a Solution I am not sure whether both the quantities will combine to from water

Can black body retain it`s absorbed heat energy? If yes, then why we can not convert this energy into a usefull form such as into electric energy as solar do?

Homework Statement If Cp for an ideal gas is 35.4 J/mol⋅K, which of the following is Cv for this gas? a. 12.5 J/mol⋅K b. 20.8 J/mol⋅K c. 29.1 J/mol⋅K d. 27.1 J/mol⋅K e. 43.4 J/mol⋅K Homework Equations ΔH = ΔE + Δ(PV) = Q + W + Δ(PV), and for ideal gas, ΔH = nCvΔT + Δ(nRT) = nCvΔT + nRΔT =...

Hi guys I know we feel infrared light as heat but my question is that is infrared a kind of light or just heat ? Thank you

Homework Statement How much heat in joules is needed to raise the temperature of 7.0 L of water from 0°C to 78.0°C? (Hint: Recall the original definition of the liter.) Homework Equations How much heat in joules is needed to raise the temperature of 7.5 L of water from 0°C to 87.0°C? (Hint...

If the universe keeps expanding and eventually ends in a "big freeze" or heat death, does this contradict the third law of thermodynamics? The third law of thermodynamics states that a crystal at absolute zero has zero entropy. Since the entropy of the universe can never decrease, as the age...

Hi guys, I am newbie on thread and currently working on a project I need some help on the Heat flow on multiple walls. Here is the setup (see figure below) The first wall is a Steel material which has a 350C temperature(1kwatts) and the an Air Gap is present then followed by a Plastic wall...

Homework Statement I'm a little bit stuck with this exercise.A small body with temperature T and emissivity ε is placed in a large evacuated cavity with interior walls kept at temperature Tw. When Tw-T is small, show that the rate of heat transfer by radiation is $$...

Homework Statement A 0.25 kg piece of ice at -30 C is warmed by an electric heater and the following graph of temperature is produced. Assume that there has been no loss of energy to the surroundings. - Use the info on the graph to determine the power output of the heater - Explain how long...

I have a long steel uninsulated cylinder filled with hydraulic fluid (let's say it's mineral oil), and I need to figure out how many barrel heaters to clamp onto it in the winter months to prevent the steel surface temperature from dropping under 40 degrees Fahrenheit. My question is, how do I...

Homework Statement A 1.75m long PVC pipe with a thermal conductivity of 0.19 W/mK has an internal diameter of 3mm and an external diameter of 5.5mm. Inner temperature is 298K and outer temperature is 273K. Calculate the heat transfer rate through the pipe and thus the decrease in the inner...

Hi all, I do an calorimeter experiment at temperatures around 40 mK. To get more grip on the time constants that are associated with the heat flows, I calculate the thermal resistance as well as the heat capitance of the materials in the set-up. We assume that Newton's law of cooling is the...

Homework Statement A steam heating system is used in winter season, The radiator of a steam heating system has a volume of 25 liters and is filled with superheated water vapor at 200 kPa and 200C. At this moment both the inlet and the exit valves to the radiator are closed. After a while it is...

A building needs a certain amount of energy during a year (kWh) for room heating. An air to water heat pump has been installed to provide heat to a radiator system (55/40°C). How do I go about estimating how much of the yearly energy need the heat pump will cover? What confuses me is that the...

Hi, I have an underwater monitor housing made out of carbon fiber and an acryllic Glass on the other side. Over time the monitor heats up. I guess carbon fiber is a bad heat conductor :(. the Acryllic glass is almost 1cm thick. Does anybody have an advice on how to cool something like this...

Hello sir, How to calculate the heat flux of titanium and aluminum?What are the essentials for doing the calculation?We are undertaking a project of multilayer coated cutting tool inserts..So we are in the need of this. Regards, Shankaralingam.

Homework Statement A problem will ask for an amount of substance in kilograms to be raised to a certain temperature and the specific heat be given in J/g*K. The amount of substance is not required to be converted to grams to match the units in the specific heat to get the correct amount of...

If I have and object at a different temperature than the thermal/heat reservoir (whatever it's called) an heat flow will take place. If I write the entropy balance for the thermal reservoir it will be: ##\frac {dS} {dt} = \frac {\dot Q} T + \dot S_{gen}## Now I remember something my professor...

Hello Physics Forum Users! I have an annoying situation with the Finite Heat Release Equation used to simulate combustion and expansion processes in an internal combustion engine. The equation is as follows: Nomenclature: P = Cylinder Pressure (kPa) θ = Crank Angle (Deg) k = Specific Heat...

Morning! My question is this: If we consider a situation of mechanical collision, in the real world we shall observe certain loss of energy into heat or sound. Can we find mathematical equations to measure the amount of sound or heat produced using only mechanical variables, such as mass...

Homework Statement The temperature distribution across a wall 0.3m thick at a certain instant of time is T(x)=a+bx+cx2, where T is in degrees Celsius and x is in meters, a = 200°C, b = -200°C/m, and c=30°C/m2. The wall has a thermal conductivity of 1W/m2K. (a) On a unit surface area basis...

Homework Statement Homework Equations Cv=(f/2)R The Attempt at a Solution I have no problem getting the right answers. My question is this: If Cv=72.254 and if Cv = (f/2)R, that implies that f = 17.381. I understand that f represents the gas particle's degrees of freedom. How does this...

Homework Statement A 529 g piece of copper tubing is heated to 89.5°C and placed in an insulated vessel containing 159 g of water at 22.8°C. Assuming no loss of water and a heat capacity for the vessel of 10.0 J/°C, what is the final temperature of the system [c of copper = 0.387 J/g · K]...

Fluid comes in at ##T_1## and comes out at ##T_2## and I know that heat is exchanged with steam at constant ##T_{steam}##. If I want to know the Surface of the exchanger then ##US(T_{steam}-T_{fluid}) = \dot m_{fluid} cp_{fluid} (T_2-T_1)## My question is, since ##T_{fluid}## changes, which...

Hi everyone, I'm currently trying to build a solar cooker which can also be used during the night / the next day so I was wondering if I can get some advice about how it can be done, especially the material that I can use to store the heat. I saw an article that said a professor from MIT had...

I have to build a small green house and to calculate if one heating wire is enough (or even too much...) Just for my curiosity I would like to understand the physics implied in this. The starting point is the desired dimensions: two modules of greenhouse with the following dimensions: 60 cm...

Hi everyone, I'm reading this paper about the solution of the heat equation inside an infinite domain: https://ocw.mit.edu/courses/mathematics/18-303-linear-partial-differential-equations-fall-2006/lecture-notes/fourtran.pdf 1) Please let me know if the following discussion is correct. The...

Homework Statement There is a waterfall 230m high, take acceleration due to gravity to be 10 m s-2 and the specific heat Capacity off water to be 4200 J Kg-1K-1 First find the speed of the water hitting before htitting the ground using the Principle of Conservation of energy Second assume all...

Homework Statement I am working on a problem where I need to determine the time taken for an air heater with an 8kW output to heat a volume of air of 9m^3 by 25C. I am neglecting all losses at the moment. It almost seems too simple in my mind that I'm concerned I'm overlooking...

hi, I met a problem about heat transfer in cylinder, if you can help, I will appreciate it. The question is simple. I want to know the transient heat distribution in a cylinder with internal heating(constant temperature not constant flux). The boundary conditions comprises two constant...

Hello Guys, I am a mechanical Engineer working on a semester project, to design a waste heat recovery system for a cement plant Air quenching cooler (AQC). For WHR i have to first design a AQC Boiler. According to the Data provided by the plant incharge, Air at the exit of cooler has a volume...

I tested it by heating it up for 2 min on a electric stove and pour about 200 to 300 ml water in bowl and did a very quick dip in and out like that and when i touch it, it was cold same temperature as the water. I also test with aluminium but when I touch it, it was will hot I burnt my finger...

I have lots of batteries 12 volt charged by the sun what I need is something that would draw 100 watts and give heat when connected to a car battery? I have ac heating pads, 2000 watt hot water elements lots of copper wire, light bulbs any other ideas?

Homework Statement You add 1500 cal of heat to a cup of water at 22.5ºC. The water has a mass of 500.0g. What is the final temperature of the water? Homework Equations Q=mcΔT The Attempt at a Solution so i tried solving it by finding the energy of the water Q=(500g)(1.0cal/g)(22.5ºC) Q=11250...

I have a practical engineering problem for which I really have no background on how to solve. I am looking for help, but don't even know what field of engineering would be likely to know the answer, so not quite sure where to ask. Any formulas that I might use to calculate the answer would...

If we have two identical objects each placed in rooms at 25°C room temperature. In the first room, the object is at 0°C. In the second room, the object is at 50°C. Which object will reach the room temperature of 25°C first?

Homework Statement In an electric circuit, consisting of copper wires with cross section area of Sc=5mm2 and a temperature of t=25C, a lead fuse is added melting when the copper wire temperature increases by Δt=25C. Find the cross section area of the lead fuse wire Sl=x. specific heat...

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Homework Statement Homework EquationsThe Attempt at a Solution Effiency of a heat pump is given as ## \eta = \frac { T_h }{T_h – T_c} = 30 ## W * 30/s = 6000*4.2 cal /s Minimum consumption rate = W/s = 840 watt Is this correct?

Homework Statement A stainless-steel wire is 0.1 mm in diameter and 1 m long. If the outside of the wire is held fixed at 20◦C, estimate the steady-state current passing through the wire when the stainless steel at the centre of the wire begins to melt.Homework EquationsThe Attempt at a...

Every year since the 90's I come back to some of my pet topics in physics, like statistical physics. This time it was the reading of a Wikipedia article on entropy that surprised me. The derivation of the second law from the Gibbs entropy was unknown to me. I didn't know how heat, how change of...

From previous threads I understand that perfectly rigid bodies cannot exist. Two, perhaps, simple questions: 1. Can atoms be stretched or compressed? 2. Does a theoretically rigid/immobile object get warm when a changing forces are applied?

When computing the rise in temperature on a body due to mechanical work, if we stick to using SI units, do we need the conversion factor called mechanical equivalent of heat. That is, can we readily equate W = Q and hence W = m x C x ΔT . Where 'm' is the mass of the substance on which work is...

Homework Statement A 2.45 kg aluminium pan at 155 C is plunged into 3.58 kg of water. If the entropy change of the system is 162 J/k, what is the initial temperature of the water? Homework Equations Q = mcΔT ΔS=mcln(T_2/T_1) Q_water + Q_Aluminium = 0 c water = 4184 J/kg*K c aluminium = 900...

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...