# the temperature at which joule thomson effect changes sign is known as temperature of

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## The temperature at which the Joule Thomson coefficient changes sign is called

See Joule Thomson effect in Comprehensive Review.The temperature at which the Joule Thomson coefficient changes sign is called

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The temperature at which the Joule Thomson coefficient changes sign is called

Text Solution Open Answer in App A

Critical temperature

B

Inversion temperature

C

van der Waals' constant

D Kelivin temperature Answer

The correct Answer is B

Solution

See Joule Thomson effect in Comprehensive Review.

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The Joule -Thomson coefficient for a gas is zero at .

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## Joule–Thomson effect

## Joule–Thomson effect

From Wikipedia, the free encyclopedia

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"Throttling process" redirects here. For the concept in computing, see rate limiting.

In thermodynamics, the **Joule–Thomson effect** (also known as the **Joule–Kelvin effect** or **Kelvin–Joule effect**) describes the temperature change of a gas or liquid (as differentiated from an ideal gas) when it is forced through a valve or porous plug while keeping it insulated so that no heat is exchanged with the environment.[1][2][3] This procedure is called a or .[4] At room temperature, all gases except hydrogen, helium, and neon cool upon expansion by the Joule–Thomson process when being throttled through an orifice; these three gases experience the same effect but only at lower temperatures.[5][6] Most liquids such as hydraulic oils will be warmed by the Joule–Thomson throttling process.

The gas-cooling throttling process is commonly exploited in refrigeration processes such as liquefiers.[7][8] In hydraulics, the warming effect from Joule–Thomson throttling can be used to find internally leaking valves as these will produce heat which can be detected by thermocouple or thermal-imaging camera. Throttling is a fundamentally irreversible process. The throttling due to the flow resistance in supply lines, heat exchangers, regenerators, and other components of (thermal) machines is a source of losses that limits their performance.

## Contents

1 History 2 Description

3 Physical mechanism

4 The Joule–Thomson (Kelvin) coefficient

5 Applications

6 Proof that the specific enthalpy remains constant

7 Throttling in the - diagram

8 Derivation of the Joule–Thomson coefficient

9 Joule's second law

10 See also 11 References 12 Bibliography 13 External links

## History[edit]

The effect is named after James Prescott Joule and William Thomson, 1st Baron Kelvin, who discovered it in 1852. It followed upon earlier work by Joule on Joule expansion, in which a gas undergoes free expansion in a vacuum and the temperature is unchanged, if the gas is ideal.

## Description[edit]

The (no heat exchanged) expansion of a gas may be carried out in a number of ways. The change in temperature experienced by the gas during expansion depends not only on the initial and final pressure, but also on the manner in which the expansion is carried out.

If the expansion process is reversible, meaning that the gas is in thermodynamic equilibrium at all times, it is called an expansion. In this scenario, the gas does positive work during the expansion, and its temperature decreases.

In a free expansion, on the other hand, the gas does no work and absorbs no heat, so the internal energy is conserved. Expanded in this manner, the temperature of an ideal gas would remain constant, but the temperature of a real gas decreases, except at very high temperature.[9]

The method of expansion discussed in this article, in which a gas or liquid at pressure 1 flows into a region of lower pressure 2 without significant change in kinetic energy, is called the Joule–Thomson expansion. The expansion is inherently irreversible. During this expansion, enthalpy remains unchanged (see proof below). Unlike a free expansion, work is done, causing a change in internal energy. Whether the internal energy increases or decreases is determined by whether work is done on or by the fluid; that is determined by the initial and final states of the expansion and the properties of the fluid.

Sign of the Joule–Thomson coefficient,

{\displaystyle \mu _{\mathrm {JT} }}

for N2. Within the region bounded by the red line, a Joule–Thomson expansion produces cooling (

{\displaystyle \mu _{\mathrm {JT} }>0}

); outside that region, the expansion produces heating. The gas–liquid coexistence curve is shown by the blue line, terminating at the critical point (the solid blue circle). The dashed lines demarcate the region where N2 is a supercritical fluid (where properties smoothly transition between liquid-like and gas-like).

The temperature change produced during a Joule–Thomson expansion is quantified by the Joule–Thomson coefficient,

{\displaystyle \mu _{\mathrm {JT} }}

. This coefficient may be either positive (corresponding to cooling) or negative (heating); the regions where each occurs for molecular nitrogen, N2, are shown in the figure. Note that most conditions in the figure correspond to N2 being a supercritical fluid, where it has some properties of a gas and some of a liquid, but can not be really described as being either. The coefficient is negative at both very high and very low temperatures; at very high pressure it is negative at all temperatures. The maximum inversion temperature (621 K for N2[10]) occurs as zero pressure is approached. For N2 gas at low pressures,

{\displaystyle \mu _{\mathrm {JT} }}

is negative at high temperatures and positive at low temperatures. At temperatures below the gas-liquid coexistence curve, N2 condenses to form a liquid and the coefficient again becomes negative. Thus, for N2 gas below 621 K, a Joule–Thomson expansion can be used to cool the gas until liquid N2 forms.

## Inversion temperature and critical temperature and Joule Thomson effect

Basics Cortical temperature: In thermodynamics, a critical point (or critical state) is the endpoint of a phase equilibrium curve. The most prominent example is the liquid-vapor critical point, the endpoint of the pressure-temperature curve that designates conditions under which a liquid and its vap

## Inversion temperature and critical temperature and Joule Thomson effect

Nikhilesh Mukherjee

### Nikhilesh Mukherjee

### Author and Consultant

Published Jun 18, 2021

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**Basics**

**Cortical temperature:**

In thermodynamics, a critical point (or critical state) is the endpoint of a phase equilibrium curve. The most prominent example is the liquid-vapor critical point, the endpoint of the pressure-temperature curve that designates conditions under which a liquid and its vapor can coexist

**Joule Thompson effect:**

The Joule–Thomson effect describes the temperature change of a real gas or liquid (as differentiated from an ideal gas) when it is forced through a valve or porous plug while keeping it insulated so that no heat is exchanged with the environment. This procedure is called a throttling process or Joule–Thomson process. At room temperature, all gases except hydrogen, helium, and neon cool upon expansion by the Joule–Thomson process when being throttled through an orifice; these three gases experience the same effect but only at lower temperatures. Most liquids such as hydraulic oils will be warmed by the Joule–Thomson throttling process.

**Concept: Different ways to explain Inversion temperature**

The inversion temperature in thermodynamics is the critical temperature below which a non-ideal gas (all gases in reality) that is expanding at constant enthalpy will experience a temperature decrease, and above which will experience a temperature increase. This temperature change is known as the Joule-Thomson effect and is used in the liquefaction of gases. Inversion temperature depends on the nature of the gas. The temperature at which the Joule–Thomson effect for a given gas changes sign, so that the gas is neither heated nor cooled when allowed to expand without expending energy is the inversion temperature. Inversion temperature is the temperature at which gas shows neither a cooling effect nor a heating effect. The Joule Thomson coefficient μ is the ratio of the temperature decrease to the pressure drop and is expressed in terms of the thermal expansion coefficient and the heat capacity. For most real gases at around ambient conditions, μ is positive—i.e., the temperature falls as it passes through the constriction. At inversion temperature Joule-Thomson coefficient µ = 0.

**Hydrogen and Helium are exceptions**

When the maximum inversion temperature is above the room temperature, then the gas can undergo any one of these cases, increase, decrease, or the same temperature on being throttled. However, there are a few gases for which the maximum inversion temperature is below room temperature. When these are throttled, there will always be only an increase in temperature, never a decrease as the Joule Kelvin co-efficient is always negative. Examples of such gases are Hydrogen and Helium. To cool these gases, first, their temperature must be reduced below their maximum inversion and then throttled

**Joule Thompson expansion of nitrogen**

.Y-axis is temperature T in kelvin and x-axis is pressure in bar. Cooling takes place in darkened area. The dotted outline of the dome represents lower inversion temperature and the continuous outline of the dome represents higher inversion temperature. The tip of the dome marked red is the inversion temperature. The temperature change produced during a Joule–Thomson expansion is quantified by the Joule–Thomson coefficient, μ. This coefficient may be either positive (corresponding to cooling) or negative (heating); the regions where each occurs for molecular nitrogen, N2, are shown in the figure. Note that most conditions in the figure correspond to N2 being a supercritical fluid, where it has some properties of a gas and some of a liquid, but cannot be really described as being either. The coefficient is negative at both very high and very low temperatures; at very high pressure it is negative at all temperatures. The maximum inversion temperature of 621 K for N2 occurs as zero pressure is approached.

**Inversion temperature and critical temperature**

Critical temp is the breaking point, regardless of the gas type, at which a temperature will increase or decrease while the gas is expanding. When a gas is released through an orifice it expands and its temperature changes, if its inversion temp is below the critical temp the temperature decreases, and if above the critical temp the temperature increases. When compressing gases to convert them into liquids, such as in the natural gas industry to get a more transportable substance, the critical temp is the point at which gas cannot be converted into liquid regardless of the amount of pressure applied. So the inversion temp is the critical temp at which the gas temp will either increase or decrease.

**Explanation**

Joule Thompson expansion is an adiabatic process. dH=∆U + PdV, U is internal energy, P is pressure and V is volume. Under the conditions of Joule Thompson expansion, the enthalpy H remains constant PdV is the work the system does while expanding at the expense of internal energy U. The decrease in internal energy produces positive Joule Thompson cooling. If the increase in kinetic energy exceeds the increase in potential energy, there will be an increase in the temperature of the fluid and the Joule–Thomson coefficient will be negative.

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