E. Zanetti | TU Delft Repository

Modeling and Optimizing Space Cooling with Solar Energy

Exploring the Potential of Ejector-Boosted and Mechanical Sub-Cooling Cycles

Master thesis (2025) - T.W.M. Peters (author) , Emanuele Zanetti (mentor) , K. Hooman (mentor) , M Ramdin (graduation committee member)

Heating and cooling systems contribute to approximately 50% of the world’s final energy consumption, highlighting their crucial role in the global energy transition. Ejector refrigeration cycles have the potential to convert heat into cooling, thereby improvi ...

Heating and cooling systems contribute to approximately 50% of the world’s final energy consumption, highlighting their crucial role in the global energy transition. Ejector refrigeration cycles have the potential to convert heat into cooling, thereby improving refrigeration sustainability. This study aims to provide a thermodynamic performance analysis of solar ejector refrigeration cycles, specifically focusing on their applicability for residential air conditioning. To provide a framework for ejector refrigeration, all components of a solar ejector refrigeration system are analyzed, detailing their fundamental principles, working mechanisms and relevant nomenclature. The emphasis of this part of the study lies on the ejector itself, including an analysis of key factors determining ejector performance such as entrainment ratios, and the definition of ejector e!ciency along with typical values.

Next, conventional and ejector refrigeration cycles are explained, highlighting the function of the ejector inside a refrigeration cycle. An overview of refrigerants, emphasizing R744 (CO2) is also included. Following this, a short review on thermodynamic ejector modeling is presented, highlighting differences and similarities across existing models in literature. Based on this literature review, two thermodynamic ejector models are developed and presented. The first model can predict the outlet saturation temperature with a maximum error of 1.54°C for known entrainment ratios. The second thermodynamic ejector is able to predict entrainment ratios and outlet pressures with an average error of 5.86% and is used for the subsequent simulations.

Three ejector refrigeration cycles are presented in terms of configuration and COP calculation. One of the presented cycles uses ejector refrigeration for mechanical sub-cooling of a R744 vapor compression cycle. A thermodynamic model is developed for both the mechanical sub-cooling cycle and a hybrid ejector refrigeration cycle to evaluate their seasonal performance. The results of this evaluation are presented through a comparative study, comparing the performance of the proposed ejector refrigeration cycles to reference vapor compression refrigeration cycles. This comparison is carried out in four distinct Koppen climate types: tropical, arid, temperate and continental. The proposed hybrid ejector refrigeration system shows a seasonal coefficient of performance (SCOP) increase between 4.74% and 18.7% across the four climate types through the use of the refrigerant R290 (propane) and a solar thermal collector area of 25 m². The mechanical sub-cooling cycle that combines R290 and R744 displays a SCOP increase between 11.3% and 25.1% through the use of a solar thermal area of 20 m². A multi-ejector design is presented to enhance performance under varying refrigerant mass flow, as well as a short economic analysis of the proposed refrigeration cycles. This research aims to form a starting point for assessing the feasibility and potential of solar ejector refrigeration cycles in residential space cooling.

About the performance of a single porous cooling fin

Master thesis (2025) - W.A. Schilders (author) , E. Zanetti (mentor) , K. Hooman (graduation committee member) , M.R. Serial (graduation committee member)

In this master thesis, an experimental study has been performed to explore if the temperature profile along a porous fin can be predicted by the existing analytical solution for solid cooling fins. The experiments performed during this thesis show that the temperature profile can ...

Design of fines separation system

Improving separation using 2D-simplified testing and coupled CFD-DEM simulation

Master thesis (2024) - E.T. van der Ven (author) , K. Hooman (mentor) , T. M.J. Nijssen (mentor) , Emanuele Zanetti (mentor)

The objective of this research is to reduce fines inside a novel comminution machine. Fines are detrimental to the energy efficiency of the comminution process and induce additional wear. An experimental setup was developed and built, the slice rig (SR), to obtain air flow measur ...

Evaluating thermal energy use in hydrogen production and import

A study on water electrolysis waste heat and ammonia cracking cold utilisation

Master thesis (2024) - M.P. Kramer (author) , K. Hooman (mentor) , E. Zanetti (mentor) , E. Khlebnikova (mentor)

In order to reach climate goals and limit global warming, an energy transition has to be made away from fossil fuels and towards renewables. Hydrogen has been recognized as having a crucial role as an energy carrier in this transition. The Port of Rotterdam in the Netherland ...

In order to reach climate goals and limit global warming, an energy transition has to be made away from fossil fuels and towards renewables. Hydrogen has been recognized as having a crucial role as an energy carrier in this transition. The Port of Rotterdam in the Netherlands has set its goals on facilitating the transition by aiming to become the 'Hydrogen Hub' of Northwestern Europe. To reach this goal, the aim is set to transport 4.6 Mt of H₂ by 2030 and 20 Mt by 2050. This will be accomplished both by hydrogen production and with import. It is expected that by 2030, 2 to 2.5 GW of (low temperature alkaline or PEM) electrolysis capacity will be installed and the rest of the hydrogen will be imported in the form of ammonia. Electrolysis produces significant amounts of waste heat and due to the storage conditions of ammonia, there is potential for cold utilisation (which is unexplored in the field of ammonia cracking). Instead of wasting this thermal energy, it would be more useful to recover and use it. Thereby potentially increasing total system efficiency and contributing to the energy transition.

The aim of this study is thus to quantify the identified thermal waste streams from water electrolysis and ammonia cracking, in order to determine how these should be reused in different applications. This will be done by using the Port of Rotterdam as a case study.

A dynamic electrolyser model was made to calculate the waste heat output as a result of fluctuating operation (due to intermittency of wind energy). A steady state thermal analysis was made of an ammonia cracking plant. Not only to determine the quality and quantity of potential cooling streams, but also to observe the effect of adding thermal energy on the ammonia cracking process (at different temperature levels). The results from these models were then used to evaluate multiple relevant and novel applications. Electrolysis waste heat modelling is applied in district heating and integration in the ammonia cracking process. Cold utilisation has been evaluated for CO₂ and H₂ compression, and for industrial cold storage.

From the different considered applications, the largest amount of electrolysis waste heat that can be reused in a single application is with integration in the ammonia cracking process. Not only can almost all the heat be directly integrated, it also creates a synergy within the hydrogen industry. This application has distinct advantages compared to other applications studied in this thesis, making it a preferred option. After that, it has been demonstrated that electrolysis waste heat can be used to provide reliable heating for a district heating network. This application is highly socially relevant, but might be a more complex option to integrate all of the waste heat. Ammonia cracking cold utilisation concluded that from a technical perspective multiple use cases are possible, however the practical feasibility must be further investigated.

This study has started to explore the potential of cold utilisation and i.e. the integration of low temperature waste heat in the ammonia cracking process. The surface of this topic has been scratched and shows results that indicate the potential it has and the need for more detailed research in this field.

Enhancing phase change material performance through the incorporation of thermally conductive objects at the solid-liquid interface

Master thesis (2024) - J.M. Amigo (author) , K. Hooman (mentor) , E. Zanetti (mentor) , René Delfos (graduation committee member) , B. J. Jan Boersma (graduation committee member)

Latent heat storage using phase change materials (PCMs) is a promising technology for storing and recovering waste heat. PCMs offer high energy density and can be tailored for specific melting temperatures, making them suitable for various applications, including temperature stab ...

Latent heat storage using phase change materials (PCMs) is a promising technology for storing and recovering waste heat. PCMs offer high energy density and can be tailored for specific melting temperatures, making them suitable for various applications, including temperature stabilization in buildings and thermal management of electronics and batteries. However, a significant disadvantage of PCMs is their low thermal conductivity, which slows the process of charging and discharging thermal energy. This work explores a novel approach to enhance the melting rate of PCMs by incorporating thermally conductive objects (TCOs) within the PCM. The TCO density lies between the solid and liquid PCM densities and is designed to follow the solid-liquid interface. First, an analytical model based on the Stefan problem formulation and a numerical model developed using Ansys Fluent, with locally modified thermal conductivity at the solid-liquid interface, were created to simulate the thermal behavior of the PCM with the addition of TCOs. An experimental setup, consisting of a rectangular enclosure with an organic paraffin as the PCM and hollow aluminum cylinders as the TCOs, was employed to validate these models under purely conductive melting conditions, with heating from the top and cooling from the bottom. Experimental results indicate that the addition of cylinders increased the melting rate by 19% under purely conductive conditions compared to the scenario without cylinders. However, the cylinders enhanced heat flux only within the first 12 mm, beyond which the thermal resistance of the liquid PCM became dominant, preventing further heat flux improvements. During solidification, the cylinders did not move with the solid front and were engulfed at the bottom. In the second part of this work, the developed Fluent model is used to study hypothetical scenarios where a TCO is added to the PCM, but heating comes from the side walls and melting is driven by convection. In this scenario, the inclusion of a TCO at the solid-liquid interface acts as a moving fin, increasing the melting rate by 62% and enhancing thermal power dissipation from 26.5 W to 75.4 W. Future research should focus on experimentally validating this scenario under convective melting, exploring methods to mechanically return the TCO to its starting position for repeatability, and conducting an energy analysis to determine whether the benefits of an enhanced melting rate outweigh the energy required to move the object and the increased manufacturing costs of the latent heat storage system.

High-Temperature Thermal Energy Storage

Master thesis (2024) - A.V. PATIL (author) , Kamel Hooman (mentor) , E. Zanetti (mentor) , J. W.R. Peeters (graduation committee member)

The study delves into the critical necessity of long-duration energy storage to ensure the consistent reliability of electricity derived from renewable sources. Numerous technologies have emerged to address this need, enabling the storage of surplus energy generated by renewables ...