Turboexpanfer joule thomson

[aamir14]

good morning you need not give a lot of details, basically right or wrong, sometimes a little explanation would be nice:

1. in a turbo-expander (used in rotating equipment to produce refrigeration temperatures at its gas exist), the turbine section is said to have free flow--what is free flow? note that the term gas turbine could be confused with a high temperature gas turbine also partially driving a compressor say in a power plant, or in a jet engine
2. it is said that because the flow is free, the turboexpander turbine will produce very low temperatures at the gas exit. this process is isentropic. why shoud an isentropic process develop low temperatures in free flow? It is also said that in free expansion, the work done is zero. If the work done is zero, how is the turbine able to drive a centrifugal compressor which is mounted on the same shaft?
3 now joule-thomson i am assuming that a joule thomson expansion (which is a throttling process) will produce a low or high tempertaure downstream of the valve, depending upon the inversion temperature. Right?
4. is it right to say that if there is a situation in Joule -Thomson that cooling takes place, that then the expansion valve is working like a small turboexpander?
5. in throttling there is always some work done right?
6. in physics does throttling refer to making the valve orifice smaller?

thank you very much

 

[Valerie Park]

1. Free flow in the context of a turbo-expander means that the gas is expanding freely in the turbine section, meaning that there is no mechanical control on the rate of expansion. This allows the turbo-expander to produce very low temperatures at the gas exit.2. In an isentropic process, the gas expands adiabatically (without exchanging heat with the environment). Since no energy is added to the system, the work done by the system is zero and the temperature of the gas decreases as it expands. The turbine is able to drive the centrifugal compressor mounted on the same shaft because the velocity of the gas exiting the turbine section is greater than that of the gas entering the compressor section. 3. Yes, a Joule-Thomson expansion will produce a low or high temperature downstream of the valve depending upon the inversion temperature.4. No, a Joule-Thomson expansion is not the same as a small turboexpander. A Joule-Thomson expansion is a throttling process whereby the pressure of the gas is reduced through an orifice, while a turboexpander is an adiabatic expansion process with no mechanical control on the expansion rate.5. Yes, some work is always done during throttling.6. Yes, throttling refers to making the valve orifice smaller.