Originally Posted by
mcamacho
Hello, Ranger1!
You are correct. Provided the installation of a pump is possible.
When a traditional ammonia chiller is used, a compressor pack is matched with an evaporator and a condenser of some sort, and they are piped together in a base frame - or site assembled. In this type of installation, the compressor pack includes an oil separator, vertical or horizontal, and enough head is allowed to install, if necessary, an oil pump.
A modern "factory" chiller is expected to minimise the ammonia charge, footprint (and costs!) using a more integral design. In our case, we use in our chillers our screw compressors with integral oil separators (similar to what you have in semi-hermetic screws), at the same time minimising external oil pipework and oil charge. We add a DX evaporator, PHE economiser, VSD drives for the motors and air cooled condenser fans. In this type of chillers, you avoid using an oil pump as it defies your main objectives. In our case, we have used differential pressures as low as 3 bar in certain projects.
Last March in Mostra Covegno, GEA presented their new water cooled ammonia chiller following the same principle of integral oil separator, combined in a semi-hermetic ammonia compressor and a flooded evaporator, so kg/kw are probably higher. Nothing wrong with this, as soon as it meets the design criteria and customer needs.
In case of dividing the load between two compressors, it is possible. However, extra is advised on the control strategy. You may end with a compressor fully loaded and another at very low partial load. So, you may (or may not!) be better off running both compressors in parallel. Again, some thought (i.e. number crunching) is required to find the best strategy.
Thank you for your comments! Have a great day!!
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