Fiberglass insulation 0.039 at 300K
It shows how the performance of fiberglass (usually a "batt" inserted in a wall or ceiling) depends on temperature. The value given above is at
approximately "room" temperature. It is common in the US to use Imperial units in which heat energy is measured in BTU, or British Thermal Units. The
conversion is not trivial, so here it is
1BTU=1055.06j
1[(W)/(m)K] is in {(:)/(f)t^(2)deg F]
What is R of a fiberglass batt that is 6 inches thick? Give two answers, one in American units based on BTUs, one in SI units based on joules.
You surely know the tale of the 3 little pigs and the big bad wolf. Which of the three little piggies picked the best insulator for their building and why? The
one who built with straw, wood or brick?
On cold day the air outside temperature is 0 degrees Celsius and the ground under the house is 10 Celsius. The optimal inside temperature for little pig
habitation is 20 Celsius. Pig Number 2 has built his house of 1-cm thick wood planks and the building is a 5 imes 5 imes 2 meter box, including the floor. What is the
heat current out of this house in watts?
Heat resistance is defined as
R=d/kA
where R is the thermal resistance,d is the path length for heat flow,A is the cross-sectional area through which the heat flows, and k is the thermal
conductivity.The temperature difference between two points separated by a barrier of thickness can be expressed as
T = T -T=qR
where q is the heat "current"the flow of energy in the form of heat.Since temperature is a measure of internal energy per particle,this equation is memorable when q is evaluated given a temperature difference and a thermal resistance.as "(flow of energy)=(energy difference)/(resistance)
In our physics system of units, thermal conductivity is given in W/m K,that is watts per meter per kelvin. Consider the thermal conductivities of
Straw 0.046
Wood 0.12
Brick 0.72
Glass(the fiber material of conventional fiberglass batt insulation) 1.0
Fiberglass insulation 0.039 at 300 K
It shows how the performance of fiberglass (usually a "batt" inserted in a wall or ceiling) depends on temperature. The value given above is at
conversion is not trivial, so here it is
1BTU=1055.06j
1 [W/mK] is 6.935 [BTU in /ft 2 oF]
1. What is R of a fiberglass batt that is 6 inches thick? Give two answers,one in American units based on BTUs, one in SI units based on joules
2.You surely know the tale of the 3 little pigs and the big bad wolf.Which of the three little piggies picked the best insulator for their building and why? The one who built with straw, wood or brick?
3.On cold day the air outside temperature is 0 degrees Celsius and the ground under the house is 10 Celsius. The optimal inside temperature for little pig habitation is 20 Celsius.Pig Number 2 has built his house of 1-cm thick wood planks and the building is a 5x5x2 meter box,including the floor.What is the heat current out of this house in watts?