Heat loss Definition and 142 Threads

I'm trying to write a very, very simple heat flow simulation program. The idea is an environment space is a grid, with each grid space identical in respect to all other grid spaces (I'm calling a grid space an "element") except temperature. So, they are physically the same except temperature...

How many watts would you need to keep a 64oz bottle of water at 40 degrees when the temperature surrounding the bottle is 10 degrees (that's assuming you don't take into account surface area) ? How many btus if you took into account the surface area of a 64oz soda bottle ? What I did...

Homework Statement If only conductive heat loss was significant for a house, then by what percentage would you lower the heat loss if the temperature was reduced inside from 70°F to 68°F, when the outside temperature is 26°F? (Hint: Try using a ratio.) Homework Equations N/A, use a...

I am building a mathematical model of a piston engine which calculates the pressure and temperature of the cylinder gas every 1° of crank angle. I'm having some difficulty with the heat transfer to and from the cylinder wall (to when the Tg > Tw and from when Tg < Tw). I found the heat...

Howdy everyone, I'm sorry if this is in the wrong forum, but since I believe it is mostly a thermodynamics problem I think this is the right arena. My questions stems from trying to insulate a bank of batteries in cold weather. I am trying to determine the proper material and design...

Homework Statement I have a manufacturing plant, and I know the material/thickness of every wall and the roof. I want to estimate the plant as an empty box, where I know the surface area of each material surrounding the box (ex. 4000 sq ft concrete, 1000 sq ft of windows, 1000 sq ft of xyz...

When we have ethanol on our skin it feels colder than when we have water on our skin. The explanation given was that more energy is required to turn one molecule of liquid ethanol to gaseous ethanol than for one molecule of liquid water. However, in that case won't more of the water evaporate...

Hi guyss~ I need some help for one of my assignment about heat loss from a cone shape fin as we can see through the picture I've attached with this thread. Looking forward to all of your answers

Homework Statement I am working on a project where I have to design and size an aquifer. There are two which either store hot or cold water for 6 months which is then pumped up to be used in either the summer or winter. The aquifer is going to be 80 meters under the ground. The rest is...

Homework Statement On a clear night the Earth loses heat according the equation \frac{dQ}{dt} = \sigmaAT4 If the average temperature of the ground is 10°C, calculate the rate of heat loss, per square metre, by the Earth and the total heat lost, per square metre, in one hour. Homework...

I'm new here. I am working on a fictional space commerce system using containers to transport things between planets. The container size is 4x4x8 meters and most often it would be colored but call it grey for the purpose of the question. I don't know what you would make it from, I suppose...

Hello all. I've been teaching myself C++ programming and had an idea for a project. I am building a calculator for the heat loss of a room when an outside door/window is open. I'm currently writing out the functions I need to make this happen... Now what I need help with is this. I can't seem to...

Hi all, i have a problem here I need to solve asap. Homework Statement I need to find out the Time it takes for 6900 gallons of WATER to go from: 55 deg F. to 32 deg F. 55 deg F. to 20 deg F. ambient air set at 20 deg F. if needed The heat loss rate is 750 Btu/Hr/degF. Homework Equations...

Hello, Homework Statement I am trying to find an expression for the energy transferred into heat due to friction between layers of viscid fluid. I am provided with the following diagram (see attachment), and am instructed to first find the force at both ends of the cylinder exerted on the...

1. An acid-base neutralization reaction is exothermic. For the measurement of the enthalpy of neutralization, for the reaction, heat is inevitably lost to the calorimeter (beaker or styrofoam cup). How will this unaccounted for heat loss affect the reported value for the enthalpy of...

Homework Statement Consider a heat pump used to heat a house to 70°F when the outside temp is 5°F. The total heat loss from the house is 10000 BTU/hr. Efficiency of the heat pump is 45% of the theoretical maximum. What will be the power used by the pump? Homework Equations e (or cop) =...

Homework Statement A plastic ice tray has a section filled with water. When placed in a coler, the water freezes into ice cubes. The mass of water is 320g and the initial temperature of water is 0 degrees Celsius. The specific latent heat of fusion is 330J/g. Pipes containing fluids are used...

Hi there, I am trying to make a spreadsheet which calculates the heat loss through a pipe and also heat loss when insulated, I am using the resistive analogy to calculate this and I have it working, the only problem I am having is the heat transfer coefficient, how do I calculate this? I...

Hi all. I am wondering how long it takes for heat to leave building. This is the example I have been working on: A building is 203m^3 and we want to raise temp from 10C to 21.3C. Vol=203m^3 => mass = 244kg (density may not be completely correct but doesn't matter) Cp=1.005 kJ/kg.k Q...

I'm creating a project where I am attempting to melt solder paste using the current running through two copper wires, in a kind of lap joint. I'm trying to figure out how much current would actually be going through the wires if I use a 9V battery. I'm not sure where to take into account heat...

Please redirect me to the appropriate forum if I have posted in the wrong place... This stuff is FAR over my head, and I need somebody with some real knowledge of thermodynamics and heat flow... I own a scuba dive shop and of course we compress air to very high pressure, on the order of 300...

I have an anaerobic digester with a volume of 2500 m^3 and internal temperature is 60°C. But, average outer temperature is 20°C. We can neglect the insulations, accept c= 1kcal/kg, and assume that the surface area of the reactor is 300 m^2. I can calculate the heat loss from e=m.c.deltaT.. Is...

I am working on a problem where I am heating a hollow cylinder from the outside with a NiCr wire which is then insulated. The pipe is cooled by running water through the center of the hollow pipe. I would like to find the heat flux transfer rate outward. So my set up from the inside to the...

Hi all, I have calculated the expected heat loss (fabric not ventilation) of a room in a house using Q=Ʃ(UAΔT) for each building element (window, door, wall, ceiling etc) making the room. The units are Watts. How can I measure the actual observed heat loss of the room? I am currently...

Hello, I am trying to calculate the heat loss of a capsule (mini submarine), size is 6m long and 0.5m radius of the ends and a height of 3m. I found a formula for calculating heat loss but it requires an R-value which I don't have, H = A(Thot-Tcold)/R (I'm guessing this is for insulated...

Homework Statement Homework Equations H=-k A \frac{\Delta T}{\Delta x} kconcrete = 1.0 W / m K (approx) The Attempt at a Solution H=\frac{-1.0 (8 * 12) (10-20)}{0.23} = 4.17 kW My problem is that the book (Essential University Physics, Wolfson) has the answer as -4.17 kW, but...

Hi, On various websites I read that 70% of the heat loss of a pool is by evaporation, whereas up to 85% of the solar radiation can heat an uncovered pool. We use 22mm thick black color EPE panels to cover our pool. On a sunny day, is it better to cover the pool or to leave it uncovered ...

Hello, I am currently studying transformer design, in particular cooling methods. I am tyring to calculate the cooling effect (increased heat transfer) of adding cooling fins to a transformer. Does anyone know of some general equations/methods for calculating the increased heat...

Homework Statement A 40-cm-long, 0.6-cm-diameter electric resistance wire is used to determine the convection heat transfer coefficient in air at 25 degrees C experimentally. The surface temperature of the wire is measured to be 150 degrees C when the electric power consumption is 90 W. If...

Hi. I want to calculate the heat which will be lost from a body at temperature 't' to the atmosphere through radiation heat transfer. I can use Stephen's Boltzmann equation, but what should i take the temperature of surroundings as? Should it be the temperature of air or space? Thanks.

Hi all, I have a system which involves a ventilated box with a heat source located inside, if the heat source inside is say 1KW and I know it eventually reaches a steady state, in an ideal world it would reach this steady state by effectively ventilating 1KW of heat through the opening and...

Hi guys, I kept trying different searches in Google and it kept bringing me to threads on this forum, so I thought it was time to join. I'm trying to calcuate the heat transferred into the environment from an air system and am having a bit of trouble... I really don't have very much...

Hi everyone. I am currently carrying out an experiment whereby I have a closed tank of water submerged in a larger tank. The water in the smaller box is heated and I am interested in the heat loss from the tank. I have done a rough theoretical calculation based on U values, where by I obtain...

Heat Exchanger! I have steam flowing past two pipes which have cold water flowing in them. I want to find out how much heat is lost from the cold water and thus the final temperature of the cold water when it leaves the pipe. I am doing this as an experiment and before I start I want to know...

A room contains 25 kg of air at 100KPa and 10 degree C. The room has a 250-W refrigerator (the refrigerator consumes 250 W of electricity when running) and 1-KW electric resistance heater. During a cold winter day, it is observed that both the refrigerator and the resistance heater are running...

Homework Statement http://img710.imageshack.us/i/2631001.jpg/ #29 Homework Equations p=I^2R P=IV The Attempt at a Solution well, the answer is D, but i don't see why the length matters? can anyone find out the equation for this problem? i thought it was B) cable B because it has...

Hi every body This question came to my mind when I was looking at a Home Heating System. The system is a closed loop. In this closed loop of pipe hot water is flowing. I know the temperature of the pipe in the beginning and at the end of the pipe. I also know the flow rate of water in the...

in the movie i was watching that is set in space, some of the characters get frozen while exposed to the vacuum of space without being properly insulated. Now i am wondering is my understanding of heat energy incorrect. I thought heat would be taken from the body by every atom that interacts...

Is there a formula for calculating heat loss due to wind (not wind chill temperature)?

Homework Statement Calculate wall loss rate in BTUs per hour. For a 10 ft by 10 ft room with an 8 ft ceiling, with all surfaces insulated to R19 as recommended by the U.S. Department of Energy, with inside temperature 68°F and outside temperature 28°F: heat loss = \frac{Q}{t} = \frac{(Area)...

I have been trying to establish what the heat loss and exit temp (in deg C) for 100ml of water traveling down a pipe located externally to a building and subjected to -10degC air temperatures will be if: The pipe has an internal diameter of 19mm and a length of 3m. 100ml of water with...

Homework Statement A pipe of radius R is maintained at temperature T. It is covered in insulation and the insulated pipe has radius r. Assume all surfaces lose heat through Newton's law of cooling \vec{J} = \vec{h} \Delta T, where the magnitude h is assumed to be constant. Show that...

Question: How much heat is lost in one hour through a 15 cm x 3.7m x 6.1m concrete floor if the inside temperature is 22 degrees c and the ground temperature is 13 degrees c? some info: thermal conductivity of concrete=1.1 change in temperature=8 Relative Equations: kAchangeT/L...

How can I determine the heat loss of person from sweating when given the weight of the person and the weight of the amount of sweat that was evaporated throughout the day?

Homework Statement Suppose that you own a poorly insulated small house, with outside walls l = 0.25m thick, total outer wall plus roof surface area 210m^2 (about 1992 ft^2) and your walls have a thermal conductivity of 1.3 W/m·K (limestone). Calculate how much power your air conditioner will...

Homework Statement A glass window pane is 2.7 m high, 2.4 m wide and 2 mm thick. The temperature at the inner surface of the glass is and at the outer surface 4°C. How much heat is lost each hour through the window? The Attempt at a Solution I have the stats on the glass like...

Does the rate of heat loss remain constant during any period. I'm doing a lab on heat loss where I'm comparing the loss of heat in a aluminum soda can with hot water to a aluminum can with hot water covered with insulation material.

I am working on an incubator/shaker for laboratory use. I am trying to work out a temperature failure and repair it, but that is besides the point here. I was looking through the user manual to try to get some clues about the failure and I came across this: "Depending on various conditions...

I'm trying to size (in watts) a heater to heat a glass of water from ambient (Ti) to a certain temperature (Tf) in a given time period (say, 1 hour). The heat-loss from the glass at Ti is 0 watts. The heat-loss from the glass at Tf is Y watts. I'm assuming that the heat loss increases...

I want to build a small geothermal cooling unit to cool one small room in my house. If i lay 0.5" pex pipe which is 0.475" ID. The big question is how long does the water flowing in the pex tubing have to stay under ground. Constant ground temperature is about 55 degrees F around my house. I...