CT: Heat-transfer fluids carry heat through solar collectors and a heat exchanger to the heat storage tanks in solar water heating systems. When selecting a heat-transfer fluid, you and your solar heating contractor should consider the following criteria:
Coefficient of expansion – the fractional change in length (or sometimes in volume, when specified) of a material for a unit change in temperature
Viscosity – resistance of a liquid to sheer forces (and hence to flow)
Thermal capacity – the ability of matter to store heat
Freezing point – the temperature below which a liquid turns into a solid
Boiling point – the temperature at which a liquid boils
Flash point – the lowest temperature at which the vapor above a liquid can be ignited in air.
For example, in a cold climate, solar water heating systems require fluids with low freezing points. Fluids exposed to high temperatures, as in a desert climate, should have a high boiling point. Viscosity and thermal capacity determine the amount of pumping energy required. A fluid with low viscosity and high specific heat is easier to pump, because it is less resistant to flow and transfers more heat. Other properties that help determine the effectiveness of a fluid are its corrosiveness and stability.
S: http://energy.gov/energysaver/articles/heat-transfer-fluids-solar-water-heating-systems (last access: 12 December 2014)
N: 1. heat (n): Old English hætu, hæto “heat, warmth; fervor ardor,” from Proto-Germanic haita- “heat”, from PIE kaid-, from root kai- “heat.” The same root is the source of Old English hat “hot” and hæða “hot weather”.
transfer (n): 1670s, “conveyance of property,” from transfer (v.).
fluid (n): “substance capable of flowing,” 1660s, from fluid (adj.). Related: Fluidal (1869), fluidic (1821, Marmaduke Tulket).
2. A liquid or gas that is used to absorb heat at some location and to surrender it after physically carrying it to some other location in a system.
S: 1. OED – http://www.etymonline.com/index.php?allowed_in_frame=0&search=heat+transfer&searchmode=none (last access: 12 December 2014). 2. TERMIUM PLUS (last access: 12 December 2014).
GV: heat transfer fluid
S: GDT (last access: 12 December 2014); TERMIUM PLUS (last access: 12 December 2014).
SYN: flowing heat carrier, fluid heat carrier medium, heat carrying fluid.
S: GDT (last access: 12 December 2014)