A post-trade aggregation system includes an allocation middleware interface, which interacts with data interface to allocate and settle trades. According to the invention it is provided that the closure element divides the reservoir into the two portions, and that the coolant is arranged in the first portion, wherein the closure element seals the first portion of the reservoir with respect to the second portion of the reservoir. Interlocking means are provided to hold the cap parts together, and seals can be provided to assure a tight enclosure.