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peadar1987
08-07-2014, 11:51 AM
Hi,

Another question about my Organic Rankine Cycle test rig.

We were wondering about the charging procedure.

The system itself is going to have a relatively large accumulator tank between the condenser and the pump.

The problem is this:

When the system is at rest, it will be charged with r245fa at slightly above atmospheric pressure. It will most likely be in the liquid phase.

When we turn on the pump and start passing fluid through the hot side of the evaporator, we're going to evaporate some fluid, but the expander is going to be filled with liquid, which isn't ideal.

Also, once some of the fluid evaporates, it's going to raise the pressure on the evaporator side.

I'm guessing this is a similar problem at start-up in pretty much all refrigerant systems, and there must be a fairly simple solution to it.

The best I've been able to come up with is to install an expander bypass, and only begin to pass the fluid through the expander when it has become a vapour. Also to charge the system with fluid at slightly less than the desired condenser pressure, so once the pressure rises from evaporating a small proportion of the fluid, we have the operating parameters we actually want.

Can anybody give any advice on this?

Many thanks
Peter