Conference Agenda

In the pursuit of sustainable energy solutions to meet the 'net zero' demands of the modern era, biogas emerges as a promising renewable resource. Derived primarily from organic waste materials, biogas offers a cleaner alternative to traditional fossil fuels. Innovative engineering solutions are necessary to realize its full potential in terms of efficiency and reliability. This research addresses this critical need by developing and evaluating the performance of an energy-efficient screw compressor designed for biogas applications. The screw compressor plays a crucial role in the biogas utilization chain, serving as both a water scrubber and membrane separator to enhance biogas purity. The key innovation lies in integrating a chamber model-based numerical simulation, providing an in-depth understanding of the compressor's performance characteristics and enabling direct comparison with an industrial conventional reciprocating compressor. The study begins with comprehensive modeling of the screw compressor using the chamber model, analyzing efficiency, reliability, and energy consumption when handling biogas. A critical aspect of the research involves a comparative analysis between the screw compressor and the widely employed conventional reciprocating compressor in industrial applications. The performance and reliability of both systems are rigorously evaluated, highlighting the advantages of the screw compressor in terms of efficiency, environmental sustainability, and long-term cost-effectiveness. Future work involves developing a prototype of the screw compressor for experimental validation.

With the recent legislation passed to reduce the effect emissions have on global temperatures causing the phase out of current third generation refrigerants, the industry has focused on creating the fourth generation with a focus on low global warming potential. Research is needed to understand how components react when these new low GWP refrigerants are used, particularly in compressors. This work quantifies the impact in compressors with an experimental analysis of R-1234yf and R-444A in a 40-ton commercial scroll compressor that was designed for R-410A, using test data collected from a hot-gas bypass compressor load stand. Tests were performed for saturated suction temperatures ranging from 20 °F to 60 °F, saturated discharge temperatures from 80 °F to 120 °F, shaft speeds from 45 Hz to 60 Hz, and superheats from 10 °F to 30 °F for a total of 22 data points for each compressor. Preliminary results show that R-410A performs significantly better in the scroll compressor than both R-1234yf and R-444A. When comparing the results to peak performance of R-410A, R-1234yf had a 11.9% point decrease in the isentropic efficiency and an 85.2% decrease in capacity, for a reduction of 13.13% in the COP. R-444A had a 12.5% point reduction in the isentropic efficiency, a 112.69% decrease in the capacity, and a 46.42% decrease in the COP when compared to R-410A.

Most of the countries around the world are adopting regulations and actions to reduce the use of hydrofluorocarbon (HFC) refrigerants with high Global Warming Potential (GWP). Among the HFCs, R134a, which has a GWP_100years equal to 1530, is recognized by the IPCC as a major contributor and its atmospheric abundances increased by 71 % from 2011 to 2019. This work presents an experimental study on the performance of a new scroll compressor performance operating with six low-GWP refrigerants as drop-in alternatives to R134a. The refrigerants used are: R1234ze(E), R152a, R516A, R515B, R450A and R513A. The system is a water-to-water chiller working with two large scroll compressors (swept volume for each compressor equal to 222.5 m³ h^-1) and two brazed plate heat exchangers as the condenser and the evaporator. The experimental tests have been conducted by fixing the inlet/outlet water temperatures in the heat exchangers when producing cold water at 7°C and 18°C. The data allow to evaluate and to assess the compressor performance in terms of volumetric efficiency and global isentropic efficiency. Numerical correlations of Pierre (1982) and Navarro et al. (2013), to estimate the compressor efficiencies, have been compared against the experimental data and new coefficients have been determined for the compressor efficiencies.

A thermal compressor uses thermal energy to increase the pressure of the working gas, while maintaining a temperature difference as an essential factor for its effective functioning. BoostHEAT's innovative thermal compressor, driven by eco-friendly thermal energy, not only targets the replacement of traditional compressors in various CO2 applications but also aligns with the critical environmental motive to address global warming. The design of the targeted thermal compressor is inspired by the gamma type Stirling engine, replacing the power piston with inlet and outlet valves[1]. This adaptation preserves some of the technical features of a Stirling engine, such as compatibility with various heating sources, low operational noise, and potential for broad applicability in today’s thermal cycles. The major attribute of this technology is the direct use of the primal thermal energy source, thus bypassing the requirement of power transmission. Another significant factor is that the thermal compressor uses the same refrigerant as the one used in the thermal cycle.

In this paper, the thermal compressor (treated as a black box) is implemented in a heat pump cycle, on which the tests were conducted. In the context of thermodynamic analysis, five principal inputs are imposed on the compressor, and five outputs are measured. These variables, which have physical significance, are crucial in characterizing the compressor and evaluating its performance. An empirical model is proposed, where each of the outputs is represented as a function of the other five inputs in a general mathematical form. The model parameters were tuned using machine learning regression methods, based on collected data. A sensitivity analysis was also carried out on each measured output with respect to the five inputs.

Overall, a CO2 thermal compressor was introduced, showing potential in both environmental and performance aspects. Based on experimental data, an empirical model was proposed, which offers both speed and reliability in predicting the compressor’s performance.

Ibsaine, R et al. (2016). Modelling of a new thermal compressor for supercritical CO2 heat pump. Energy, 117, 530-539.

With the implementation of Kigali Amendment, R290, as a natural refrigerant, has become more and more popular in many applications. For example, in room air conditioner. Compared with recently widely used R32 or R410A in this application, R290 has lower per-unit cooling capacity of swept volume. It means the displacement of R290 compressor need to be bigger than that of R32 or R410A compressor, which will increase the cost of compressor significantly. Another effective way to meet the cooing capacity requirement is to improve the rotational speed of R290 compressor. However with the improvement of rotational speed, there are many challenges for compressor performance and reliability related to compressor structure and key components. In this paper we'll discuss these issues and find out the way to solve these problems. After discussions, some conclusions will be made for the design of a high speed R290 compressor.