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A Novel Loop-Heat-Pipe (LHP)-based Data Centre Heat Removal and Recovery System Employing the Micro-channels Cold/Hot Plates

Periodic Reporting for period 1 - LHP-C-H-PLATE-4-DC (A Novel Loop-Heat-Pipe (LHP)-based Data Centre Heat Removal and Recovery System Employing the Micro-channels Cold/Hot Plates)

Reporting period: 2019-09-09 to 2021-09-08

A data centre, comprising buildings, services and data processing equipment, is a functional space consuming tremendous amount of energy. The data centres are estimated to consume 1.1- 1.5% of the world’s total electricity supply and be responsible for around 0.5% of the world carbon dioxide emission, with an annual power demand increase rate of 15-20%. Space cooling (i.e. air conditioning) is a fundamental need of data centres which, aiming to removing tremendous amount of heat dissipated from the data processing equipment and keeping space air temperature to an adequate level, consumes more than 40% of energy delivered into the data centre. The current situation is that the heat generated from data processing equipment (e.g. server racks, processors, memory chips etc.) is mostly dissipated into the data centre space; this creates an extremely high cooling load (around 400 W/m 2 ) which needs to be tackled by the centralised, mechanical vapour compression based air conditioners. Owing to the high cooling load and continuous operation of the air conditioning system all year round, the energy (electricity) consumption of the data centre is huge. To cut off the cooling loads of data centre spaces is very important for the sustainable development of society.
The overall objectives of the programme were: (1) a novel LHP-C-H-PLATE-4-DC which can effectively remove and reuse the heat from the data processing equipment, thus significantly reducing the cooling load of the data centre and energy consumption of the installed mechanical air conditioners and heating systems; and (2) a computerised analytical and optimisation model for the LHP-C-H-PLATE-4-DC using the latest fractal theory and enthalpy/temperature-difference-driven heat and mass transfer theory.
Firstly, the conceptual design of the LHP-C-H-Plate-4-DC system was carried out by consulting a large number of documents. A series of work had been carried out to construct schematic diagrams of system components and integrated units, evaluate geometric dimensions and material types as well as potential performance data, and determine basic research questions and projects.
Secondly, using the latest fractal theory and related research results, the relationship between the fractal dimension and the porosity of porous media was established. By applying Darcy's law, the calculation formulas for the permeability and effective thermal conductivity of the core heat pipe were established. By calculating the criterion parameters of vapor and liquid fluids, including Re number, Pr number and Nu number, and using the macro heat transfer equation, the heat transfer rate and pressure loss under different operating conditions could be obtained. Based on these, a computer model was built, which could determine the optimal geometric dimensions of the system and predict the LHP-C-H-Plate-4-DC system performance.
Thirdly, the LHP-C-H-Plate-4-DC prototype was constructed and tested at the Energy Technology Laboratory at University of Hull. Using the method of controlling variables, the system performance changes under different parameter conditions, such as simulated heat load, coolant water temperature, coolant water flow rate and refrigerant filling ratio, were tested and obtained. After experimental testing, it was found that under the best experimental conditions, namely the simulated heat load of 500W, the coolant water flow rate of 600L/h, and the coolant water temperature of 15℃, and the refrigerant filling ratio of 30%, the system had the highest heat recovery efficiency of 86.28%. In addition, comparing the test results with the simulation results, the errors was less than 15%, which were acceptable for general engineering applications, indicating that the established model can predict the performance of the LHP-C-H-Plate-4-DC system at a reasonable accuracy.
Fourthly, the performance of the LHP-C-H-PLATE-4-DC data center cooling system was evaluated according to the climate conditions in Europe, and the capital cost and annual operating cost of the new system in different European regions were calculated. The results were also compared with the cooling system without LHP-CH-PLATE-4-DC, and the estimated payback period and carbon dioxide emission reduction of the new system relative to the existing cooling system were obtained.
In addition, two papers were published while four manuscripts were currently under review/about to be accepted. Furthermore, 4 international conferences were attended online in countries such as UK, and China, and professional connections were made in each conference. At each of these conferences, presentations were made on the project topic and subsequent discussions with interested researchers were performed.
The proposed programme provided an innovative heat removal and recovery technology which can significantly reduce the cooling load of data centres and energy consumption of the installed air conditioners within data centres.Combining calculations with climate data from Belgium, the UK, Italy, Finland, Poland, and Portugal, it was concluded that the investment payback period of the programme was 2.3 years, 1.9 years, 2.2 years, 1.8 years, 2 years and 2.3 years respectively, and the annual carbon emissions that the programme can reduce were 1765kg, 2183kg, 1813kg, 2257kg, 1993kg and 1790kg. After comparison, the proposed programme can reduce carbon dioxide emissions, reduce data centre energy consumption, improve the working conditions of European data centres and contribute to the development of the EU economy.
Further benefits to the ERA are: (1) promoting transfer of knowledge and technology; (2) attracting international human resources to the European science and technology; (3) making Europe the major centre of attraction to researchers from all over the world and formation of a single labour market; (4) widening the recruitment opportunity and increasing the portability of grants; and (5) helping the industry to develop a partnership with the research centres of excellence.