In the agricultural and work machine sectors, hydromechanical transmission competes with traditional mechanical transmission. However, the double energy conversion taking place in hydrostatic transmission lowers the efficiency of the entire transmission. Thus, the dimensioning of hydromechanical transmission must not only meet the functional requirements of speed and power to be transmitted, but must also identify the particular combination of layout and the components that leads to the maximum efficiency. In this study, a general answer to this problem will be given. The design is transformed into a mathematical programming problem, whose goal is the optimisation of both the configuration and internal components of the transmission. The structure of the transmissions is described by means of graph theory, and the resolution of the optimisation problem is obtained by means of a ‘direct search’ algorithm based on the swarm method.

Heating, Ventilation and Air Conditioning (HVAC) systems must be specifically designed for Operating theaters in hospitals, in order to reduce the risk of infections and maintain adequate thermo-hygrometric conditions. New design procedures of operating theaters can benefit from the results obtained by properly validated Computational Fluid Dynamic models. In fact, CFD models allow to obtain local information inside the room, without carrying out complex experiments, with consequent reduction of the costs required for testing ventilation systems. In this work, a novel procedure for validation of numerical simulations of airflow distribution in actual operating theaters is presented. The authors designed and carried out an experimental campaign in a new operating theater, to measure airflow distribution near the surgical site, and validate a novel numerical model with specific reference to the inlet flow conditions. The results prove that the present approach is essential to reproduce the actual flow conditions inside operating theatres, and clearly shows the influence of flow boundary conditions on the numerical solution of air velocity in the room.

This paper presents a reversible heat pump based on CO₂ as the refrigerant, able to provide heating, cooling, and domestic hot water to high energy demand buildings. The unit was developed and tested under the EU H2020 project MultiPACK, which has the main goal of assuring the market about the feasibility, reliability, and energy efficiency of CO₂ integrated systems for heating and cooling and promoting a fast transition to low environmental impact solutions. Within the project, the confidence raising was performed by installation and monitoring of fully integrated state-of-the art CO₂ systems in the Southern European Climate. With the aim of predicting the unit behaviour under variable load and boundary conditions, a dynamic model of the entire unit was developed with commercial software, considering actual components and the implemented control system and it was validated with experimental data, collected at the factory’s lab before commissioning. The validation against experimental data collected during operation as a heat pump demonstrated a maximum percentage difference between the experimental and predicted value of gas–cooler heat flow rate equal to +5.0%. A preliminary comparison with the experimental data in chiller configuration is reported, however further development was required to achieve a satisfactory validation. Lastly, the numerical model was utilized to simulate a typical operation in heat pump configuration with the system coupled with a hot water tank storage for the production of domestic hot water and space heating; the model predicts higher COP when operating in domestic hot water operation due to the lower water inlet temperature.