Abstract This paper presents a new heat pump unit intended to provide heating, cooling and hot water to a hotel and using CO 2 as the working fluid. The heat pump was installed in mid-2018 in a hotel located in a touristic area in North Italy and open nearly all over the year. The unit can benefit from ground water as heat source or heat sink. The heat pump features a two-phase multi-ejector as expansion device. An original two-evaporator lay-out is implemented, where the first one is gravity driven and the second one is ejector driven. It is fully equipped with measurement instruments, data acquisition system and cloud data storage, developed and tailored for the unit. The unit was developed, instrumented, installed and monitored within the H2020 MultiPACK project, which aims at building confidence in integrated heating, ventilation, air conditioning and refrigeration packages based on CO 2 technology in high energy-demanding buildings. In this paper, operational parameters and performance data will be presented, related to winter season, thus to heating and domestic hot water service.
The ejector technology, which is by now sufficiently developed to be used in industry, opens the door to the efficient use of CO2 as a refrigerant in air conditioning and space heating applications, where the sink temperature ranges from 30 to 40°C. The experience gained in commercial refrigeration can be immediately transferred in the new application, thus eliminating major technical barriers. In the proposed layout the ejector, recovering part of the expansion energy, is used to overcome the efficiency penalization occurring at high heat sink temperature, which may happen both during space heating operations (wintertime) and cooling operations (summertime), when outdoor temperature is particularly high. The aim of this paper is to present the energy assessment of a water/water R744 chiller/heat pump, working according to an ejector transcritical cycle, used for winter heating, summer cooling and tap water production. For simplicity reasons, the different functions (heating, cooling, water heating) are managed on the water side and therefore no inversion between the evaporator and gas cooler role is required. Results can nevertheless be extended to reversible units, which, however, require a specific development, as no units are currently available on the market. Energy consumption is compared with that of the reference system, working according to a simple cycle with internal heat exchanger, showing a total energy saving of 15% on an annual basis at the assumed conditions for space heating and cooling. Simulations are performed in a typical climate condition of Northern Italy for a residential family house. Technical considerations about the proposed layout are presented.
This paper describes the development of a CO 2 air/water heat pump, designed to meet the tap hot water requirement of a residential building located in the northern part of Italy. The basic design consists of a single-stage piston compressor, a coaxial type gas cooler, an electronic expansion valve, a finned tube evaporator and a low pressure receiver. The heat pump is combined with a storage tank designed to maintain internal water stratification . A new control method for the upper cycle pressure was developed to maximise the COP of the heat pump, while the water mass flow is adjusted to maintain the set water temperature at the gas cooler exit. Before commissioning, the heat pump was factory tested to verify its energy performance and to validate the high pressure control logic.
