Heat exchanger modelling

TRI-HP EU project aims to develop trigeneration integrated solutions that combine heating, cooling and electricity
generation based on heat pumps running with natural refrigerants and using multiple renewable energy
sources. Most of the developments of the project are focussed on the whole refrigerant cycle of the heat pumps
as well as on the heat exchangers used. Three innovative heat exchangers have been designed, manufactured,
and tested as stand-alone devices and implemented in heat pumps with nominal capacities of 10 kW within
the current project. The experimental results of the supercoolers have been published in [1] where all experimental data used here is accessible as open data.
One of the heat exchangers developed is based on brazed heat exchangers where icephobic coatings have been
applied to achieve high levels of supercooling in very compact heat exchangers typically used in residential heat
pumps. Several coatings were applied into plate heat exchangers, the so-called supercoolers, and were compared
to each other. The best coatings were applied in the evaporators of the heat pumps that were able to supercool
water in real dynamic conditions. In the present deliverable, a numerical model to predict the behaviour of supercoolers
is presented and validated with experimental data. Results show that the model presented here is able
to capture the main characteristics of the supercoolers assessed. The experimental results of the dual source/sink heat exchanger have been published in [2].
A second innovative heat exchanger is a dual source/sink unit able to use brine/water as well as air as heat sources
and sinks for heating and cooling, respectively. The idea is to be able to use ground sources as well as ambient air
as heat sources and sinks. This heat exchanger is key in the development of a dual source/sink heat pump which
has been manufactured and tested. This hybrid heat pump is fully reversible, and as such, the dual heat exchanger
needs to operate as an evaporator as well as a condenser. The design and sizing of this heat exchanger were based
on a numerical model developed in Modelica. The numerical model, as well as its validation in heating and cooling
models using both sources, is provided. 
The third innovative heat exchanger is specially dedicated to transcritical CO₂ heat pumps. A tri-partite gas cooler
has been developed to provide space heating (SH) and domestic hot water (DHW) simultaneously in a
compact unit. The tri-partite gas cooler consists of three brazed heat exchangers connected in a particular form.
The first gas cooler is used to preheat DHW, the second one is used to provide SH, and the third one is to reheat
DHW. The three gas coolers are connected in series on the CO₂ site such that the hottest part of the CO₂ side is
connected to the third gas cooler. The CO₂ is then cooled from the gas cooler third to the one. experimental
results of the tri-partite gas coolers have been published in [3].