Ammonia charge reduction potential in recirculating systems – calculations.

This paper focuses on the effect of changing the circulation rate for industrial evaporators and presents calculation method for estimating the ammonia liquid hold-up in the evaporator. This paper is the first part in a series of two. The second paper [10] applies the results of this paper to evaluate the influence of controlling the circulation rate on selected industrial refrigeration systems for a distributed cold storage. To make accurate calculations of the charge of such a system in the future, a new calculation method must be developed. Laboratory measurements have been conducted on three types of evaporators to measure the capacity and liquid hold-up for various circulating rates. The measurements combined with simulations and current design rules for non-controlled recirculating systems are used to create new methods of calculating the refrigerant charge and find the possible reduction in the circulation rate without affecting the capacity.