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The R-value is the building industry term [3] for thermal resistance "per unit area." [4] It is sometimes denoted RSI-value if the SI units are used. [5] An R-value can be given for a material (e.g., for polyethylene foam), or for an assembly of materials (e.g., a wall or a window). In the case of materials, it is often expressed in terms of R ...
The Lankford coefficient (also called Lankford value, R-value, or plastic strain ratio) [1] is a measure of the plastic anisotropy of a rolled sheet metal. This scalar quantity is used extensively as an indicator of the formability of recrystallized low-carbon steel sheets.
Conversely, thermal resistance (R) measures the opposition to the heat current in a material or system. It is measured in units of kelvins per watt (K/W) and indicates how much temperature difference (in kelvins) is required to transfer a unit of heat current (in watts) through the material or object.
Typical R-values are given for various materials and structures as approximations based on the average of available figures and are sorted by lowest value. R-value at 1 m gives R-values normalised to a 1 metre (3 ft 3 in) thickness and sorts by median value of the range.
The letter R was chosen because visually it loosely resembles the Ω glyph, and also because it works nicely as a mnemonic for resistance in many languages. [ citation needed ] The letters G and T weren't part of the first issue of the standard, which pre-dates the introduction of the SI system (hence the name "RKM code"), but were added after ...
These first Heisler–Gröber charts were based upon the first term of the exact Fourier series solution for an infinite plane wall: (,) = = [ + ], [1]where T i is the initial uniform temperature of the slab, T ∞ is the constant environmental temperature imposed at the boundary, x is the location in the plane wall, λ is the root of λ * tan λ = Bi, and α is thermal diffusivity.
A multi-family residential building under construction with rigid panel exterior insulating sheathing. Rigid panel insulation, also referred to as continuous insulation, [1] can be made from foam plastics such as polyurethane (PUR), polyisocyanurate (PIR), and polystyrene, or from fibrous materials such as fiberglass, rock and slag wool.
The basic unit of insulation coefficient is the R SI, (1 m 2 ⋅K/W). 1 tog = 0.1 R SI. There is also a US clothing unit, the clo , equivalent to 0.155 R SI or 1.55 tog, described in ASTM D-1518. [ 7 ]