Correct Answer - Option 2 : Pour point
Explanation:
Lubricant:
With the movement of the two mating parts of the machine, heat is generated. If it is not controlled the temperature may rise resulting in total damage of the mating parts. Therefore, a film of cooling medium with high viscosity is applied between the mating parts which are known as a lubricant.
Pour point: The pour point in that temperatures just about which the oil sample will not flow under certain prescribed conditions. In other words, pour point of a liquid is the temperature below which the liquid loses its flow characteristics. Hence, If the lubricant for an automobile to be used under sub-zero temperature the pour temperature is considered on priority.
Calorific value:
- The calorific value (CV) or heat value of solid or liquid fuel is defined as the amount of heat given out by the complete combustion of 1 kg of fuel.
- It is expressed in terms of kJ/kg.
- The calorific value of gaseous fuel is expressed in terms of kJ/m3 at a specified temperature and pressure.
Specific gravity:
The relative density/specific gravity of a substance is defined as the ratio of the density, mass or weight of the substance to the density, mass or weight of water at 4° C
\(Relative\;density = \frac{{Density\;of\;substance\;}}{{Density\;of\;water\;at\;4^\circ C}} \approx \frac{{Mass\;of\;substance\;}}{{Mass\;of\;water\;at\;4^\circ C}} \approx \frac{{Weight\;of\;substance\;}}{{Weight\;of\;water\;at\;4^\circ C}}\)
Here relative density is unitless and the density of water at 4° C is 1.0×103 kg/m3
Whereas density, \(\rho = \frac{{Mass}}{{Volume}}\)
Properties of lubricant
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Viscosity
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It is the fluidity of oil by which it can withstand high pressure or load without squeezing out from the bearing surface
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Oiliness
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Oiliness refers to a combination of wettability, surface tension, and slipperiness.
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Flashpoint
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It is the temperature at which the vapor is given off from the oil.
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Fire point
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It is the temperature at which the oil catches fire and continues to be in flame
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Pour point
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The temperature at which the lubricant is able to flow when poured
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Emulsification
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It indicates the tendency of an oil to mix intimately with water to form a more or less stable emulsion.
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