Tests with liquid and solid fuels in model tunnels (1:20) were performed and analysed in order to study the effect of tunnel cross section (width and height) together with ventilation velocity on ceiling gas temperatures and heat fluxes. The model tunnel was 10m long with varying width (0.3m, 0.45m and 0.6m) and height (0.25m and 0.4m). Test results show that the maximum temperature under the ceiling is a weak function of heat release rate (HRR) and ventilation velocity for cases with HRR more than 100MW at full scale. It clearly varies with the tunnel height and is a weak function of the tunnel width. With a lower tunnel height, the ceiling is closer to the base of continuous flame zone and the temperatures become higher. Overall, the gas temperature beneath the ceiling decreases with the increasing tunnel dimensions, and increases with the increasing longitudinal ventilation velocity. The HRR is also an important factor that influences the decay rate of excess gas temperature, and a dimensionless HRR integrating HRR and other two key parameters, tunnel cross-sectional area and distance between fuel centre and tunnel ceiling, was introduced to account for the effect. An equation for the decay rate of excess gas temperature, considering both the tunnel dimensions and HRR, was developed. Moreover, a larger tunnel cross-sectional area will lead to a smaller heat flux.

The energy network in Luleå consists of the steel plant, heat and power production and district heating. Global system studies are necessary to avoid sub-optimization and to deliver energy and/or material efficiency. SSAB began work with global simulation models in 1978. After that several more specialized process integration tools have been tested and used: Mathematical programming using an MILP method, exergy analysis and Pinch analysis. Experiences and examples of results with the different methods are given and discussed. Mathematical programming has been useful to study problems involving the total system with streams of different types of energy and material and reaction between them. Exergy is useful to describe energy problems involving different types of energy, e.g. systematic analysis of rest energies. Pinch analysis has been used especially on local systems with streams of heat energy and heat exchange between them.

An increased use of heat pumps is one of the measures that can be taken to reduce energy consumption on a large scale. For a wider acceptance, and major heat pump market expansion, it is crucial to develop heat pumps that cause minimal disturbance. Results from field measurements made by SP Technical Research Institute of Sweden indicate that the use of indirect heat pumps has potential to significantly reduce the outdoor noise level of ambient air heat pumps. The noise level caused by such heat pumps has been shown to be highly influenced by the design of the air-to-fluid heat exchanger. The overall purpose of this study is to propose a design of an air-to-fluid heat exchanger that allows for a well performing system as well as a low level of noise and cost. Two different types of heat exchangers, with flat tubes and round tubes, are compared theoretically. According to the modelling results, a heat exchanger with flat tubes and plain fins is the most suitable out of the studied designs due to its low heat transfer resistance on the tube side. The round tube heat exchangers showed to be significantly less suitable, displacing more than twice the volume.

The steel industry has faced several challenges during the years. There has always been an aspiration towards higher economic profitability for the system. During the mid 1970s and 1980s the energy crises caused a dramatic rise in energy costs, which led to an increased awareness in energy conservation. In recent years, climate change issues have become more important for the industry. The operating practises for an industrial system are often affected by external restrictions concerning the economical, energy and environmental efficiency of the system. There are a large number of ways to increase the system efficiency, e.g. installation of new process equipment, and practice changes. However, industrial systems such as an integrated steel plant consist of a system of several processes connected together with product and by-product interactions, where changes in one unit may result in changes throughout the total system. A process integration method focusing on the total integrated steel plant system by a simultaneous approach is adopted. An optimisation model is developed and used to study the effect of changes in the existing material and energy system. Applications of the model on the energy and material system have been made. The model can be used to analyse energy, environmental and economic aspects making it a powerful complement as a decision making tool. Conclusions about energy, environmental and economic effects are presented. © 2005 Elsevier Ltd. All rights reserved.

The impact of impulse technology on a system-wide level has been investigated in this study for non-integrated fine paper and linerboard mills. Impulse unit data were obtained from STFI's EuroFEX research paper machine and correlations were developed in order to predict performance (dewatering, electricity consumption) under commercial operating conditions. Mill analyses were conducted for different configurations (i.e. one or two impulse units with and without web preheating) operating with roll temperatures of 200-320 °C. Results show that the ingoing dryness to the dryer section can be increased within a wide span, from 7 to 27 percentage points depending upon the grade and operating parameters. Even though electricity consumption rises dramatically from the inductively heated rolls, overall fuel savings of up to 20% can be achieved with either one or two impulse units operating at 200 °C (external power plant efficiency assumed to be 45%). Impulse technology appears to be neutral in terms of production costs since increases in energy costs are expected to be counterbalanced by savings in feedstock materials and enhanced product quality. Estimates show that this technology can lead to substantial reductions in dryer section sizes for new installations or alternatively enhance productivity in existing paper machines. 

Electrohydrodynamic (EHD) air blowers are uniquely positioned to overcome the limitations of miniaturized mechanical fans in small-scale and consumer electronic devices. A novel cooling system design using optimized EHD blowers integrated with a plate-fin heat sink is presented and proposed for thin consumer electronics such as laptop applications. A three-dimensional (3D) numerical model is developed and validated to solve the coupled equations of EHD flow and conjugate heat transfer and predict the cooling performance of the integrated EHD system. For a range of heat sink heights from 6 to 12 mm, a parametric study is performed to investigate the influence of geometric parameters and operating conditions on the thermal performance of the EHD systems based on heat sink thermal resistance and the highest operating temperature. Numerical results demonstrate that the proposed EHD cooling system is able to provide effective cooling performance and maintain the temperature within the safe and typical operating range. Under a range of thermal design power (TDP) up to 30 W, trends of predicted operating temperatures show that the developed EHD cooling systems have great potential to compete with mechanical blowers in low-profile laptops with higher TDP, lower device height and reduced installation volume compared to a selected list of current standard laptops available commercially.

Server power densities are foreseen to increase, and conventional air-cooling systems will struggle to cope with thermal demand. Single-phase immersion systems are a promising alternative to operate very intensive workload such as high-performance computing, cryptocurrencies mining or research activities. However, few companies deal with this kind of system and there is a lack of energy models that can reproduce an accurate analysis of the system behaviour. This study addresses the experimentation, data collection, and model validation of a single-phase immersion cooling system where 54 open compute project servers, each with a peak power of 400 Watts that are submerged and operated in a dielectric coolant. Results show the evolution of the thermal profile of the system under static and dynamic workloads, and it provides a correlation of server energy use under various system temperatures. The energy model is presented, validated against real data, and exploited to investigate the system response to different cooling conditions. In conclusion, the study demonstrates the validation of the energy model and supports the basis for further investigation. © 2023 The Authors

The non-isothermal thermogravimetric analysis was conducted to evaluate the combustion characteristics of Yangquan anthracite coal (YQ), palm kernel shell char (PC) and their blends with different mass ratios. The physical and chemical characteristics of YQ and PC were also studied systematically. The investigation shows that, compared to YQ, PC was more reactive due to the higher content of the alkali metal oxides, lower ordering degree and more developed porous structures. The combustion reactivity of YQ can be improved effectively by mixing with PC, and a synergetic effect between YQ and PC can be observed. The experimental results of the thermal degradation experiments were represented with both the random pore model (RPM) and the volume model (VM), and the activation energies and pre-exponential factors were further determined. The performance of the RPM model is slightly better than that of the VM model. The activation energies of all samples are in the range of 90.2–121.8 kJ/mol, where the lowest value of 90.2 kJ/mol is for the sample of PC at 60% mass ratio.