absolute temperatrure scale

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Absolute TemperatureScale

Group # 02

09-NTU-1057 09-NTU-105909-NTU-1058 09-NTU-1060


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Temperature

Temperature is physical property of matter that quantitative expresses the

common notions of the hot and cold

Objects of low temperature are cold, while various degrees of higher

temperatures are referred to as warm or hot

Heat flows from hotter bodies to cooler bodies, until equilibrium is

attained

Temperature is measured with thermometers, which may be calibrated to

a variety of temperature scales


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Absolute Temperature Scale

A temperature scale having absolute zero as the lowest temperature

Absolute temperature scales only have positive numbers

No negative values in absolute temperature scale

Usually refer to

Kelvin Scale

Rankine Scale


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Kelvin Kelvin is not referred to or typeset as a degree

Kelvin is the primary unit of measurement in the physical sciences

Often used in conjunction with the degree Celsius, which has the

same magnitude.

Subtracting 273.16 K from the triple point of water makes

absolute zero equivalent to 273.15 C


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Kelvin Temperature Conversion formulae


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Rankine Scale

Proposed in 1859 after Kelvin Scale

Named after the Glasgow University engineer and physicist William

John Macqourn Rankine

The symbol for degrees Rankine is R

Rankine degree is defined as equal to one degree Fahrenheit

temperature of 459.67 F is exactly equal to 0 R


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Rankine Scale

Some engineering fields in the U.S measure thermodynamic

temperature using the Rankine scale

Freezing point of Water is 491.67 R

Boiling point of Water is 691.64102 R

Triple point of Water 491.688 R

In thermodynamics, the triple point of a substance is the

temperature and pressure at which the three phases (gas, liquid, and

solid) of that substance coexist in thermodynamic equilibrium


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Rankine Temperature Conversion formulae


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Temperature Measuring Devices

Thermocouples

Thermistor

Resistance temperature resistance

Pyrometer

Langmuir probes(for electron temperature of a plasma)

Infrared

Thermometer


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Comparison

One of the problems with the Celsius and Fahrenheit scales is that they are

not linear

We cannot say, for example, that a cup of water at 40 degrees C is twice as

hot as one as 20 degrees, or that water at 20 degrees is twice as hot as water

at 10 degrees.

The absolute or Kelvin scale solves this problem, because it is linear


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Kelvin Temperature scale

Assigned temperature values should independent of the properties of any

thermometric substance, these considerations lead to Kelvin temperature

scale

Kelvin scale provide a continuous definition of temperature of

temperature connecting the several connecting empirical methods for

assigning temperatures

Kelvin scale also plays an important role in developing aspect of the

second law, including the evaluation of maximum performance measures

for cycles in the next section


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Cont.

This eq. provide a basis for defining thermodynamic temperature scale,

Scale independent of the properties of any substance

Kelvin scale is obtained by making a particularly simple choice

= Tc/TH

Tis the symbol to denote temperature on Kelvin scale


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Kelvin scale has a zero of 0k, and lower temperatures are not defined

Temperature of zero on the Kelvin scale is the lowest conceivable

temperature, this temperature is called absolute zero

So, Kelvin scale is called an Absolute Temperature scale

This scale is valid for all possible ranges


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International Temperature Scale(ITS)

To provide a standard for temperature measurement taking into account both

theoretical and practical considerations, International temperature scale(ITS)

is adopt in 1927

This scale is then refined and extended in several revisions in 1990

ITS is defined in such a way that the temperature measured on it conforms

with the thermodynamic

Unit of ITS is Kelvin


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The ITS-90 is based on the assigned values of temperature of a number of

reproducible by formulas that give the relation between readings of standard

instruments and values of the ITS

The range from 0.65 to 5.0 k is defined by equations giving the

temperature as function of vapour pressures of particular helium isotopes

Range from 3.0 to 24.5561 is based on measurements based on a helium

constant-volume gas thermometer


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Range of 13.8033 to 1234.9 k is defined by mean of certain

platinum resistance thermometers

Above 1234.9 k the temperature is defined using Planks equation

for black body radiation and measurement of the intensity of

visible-spectrum radiation


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absolute temperatrure scale

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