VISCOSITY:
Resistance to flow About 32-36 cSt at 40 C.
High viscosity:-
- Loads pump motor, especially during cold start
- Pump motor sized for cold starting
- Also, poor heat transfer
Useful when:-
- Selecting thermic fluid for low ambient temperatures
- Checking condition – Oxidation increases viscosity
SPECIFIC GRAVITY:
- Normally around 0.9 at ambient temperature.
- Reduces with increase in temperature – approx. 0.7 at 300 C.
This means-
For TF :1 bar = 14 MLC (Meter of Liquid Column)
SPECIFIC HEAT:
Quantity of heat required to heat unit mass through unit temp. difference, at a given temperature
About 0.45 at 30 C., 0.7 at 300 C.
Unit : Kcal/Kg C
This can be used when:
- Relating thermic fluid flow and delta T
- Estimating heat transferred in process
FLASH POINT:
- Minimum temperature of fluid at which vapors just above surface of fluid ignite with a flash when shown a naked flame or a spark. The flame is not sustained, since the vapors are not replaced fast enough from fluid surface.
- It is measured using a standard size cup.
- This indicates ignitability of vapors formed during heating of oil & presence of easily ignitable constituents of oil.
- Flash Point of fresh oil – 200 - 215 Deg C.
- Flash point of a thermic fluid held at high temperature keeps falling.
FIRE POINT:
Minimum temperature of fluid at which vapors just above surface of fluid ignite when shown a naked flame or a spark and the flame is sustained since vapors are replaced fast enough from fluid surface.
It indicates that fluid has cracked more and is generating more vapors than at Flash Point.
BOILING POINT:
Temp. at which change of phase takes place.
Boiling point varies from 330 to 371Deg C, depending on the brand.
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