Abstract

Flue gas recirculation (FGR), which is adopted to control the reheat steam temperature of double-reheat boilers, significantly affects the temperature, heat flux and NOx distributions. The effects of FGR on combustion characteristics and heat flux distributions were investigated by numerical simulation on 660 MW tower-type double-reheat boiler. The results show that, the FGR could reduce the temperature in the furnace under boiler maximum continuous rating (BMCR), 70% turbine heat acceptance (THA) and 50% THA loads. With the injection of recirculation flue gas (RFG), the heat flux in the combustion zone decreases, more heat is transmitted to the upper part of the furnace. The peak value of wall heat flux appears near the center line of furnace wall. The NOx emission increases with the decline of boiler load and the FGR technology could effectively reduce the NOx emission.

Abstract

In this study, a method for the monitoring of telecommunication central offices (COs) is proposed with the purpose of classification in terms of efficiency and diagnosis of anomalous energy consumptions. The objective is achieved through the definition of new indices based on the energy spent by the telecommunication and cooling systems, improving the outcomes of pre-existing methods. While the reliability index and the index of cluster reliability check the ratio between the telecommunication (TLC) and climate control (CLC) energy consumption, the coefficient of variation adds a check on the reliability of TLC-energy measurements. Another target of this study is to extend the analysis to multi-annual periods of monitoring, thus allowing successfully meeting the currently in-force ISO50001 standard for what concerns with the continuous monitoring of industrial plants (including the TLC sector) towards the achievement of sustainable and energy efficient enough operation. After the presentation of the method, specific central offices were selected and further analyzed to fully verify the results match the physics of the energy consumptions behavior.

Abstract

The main aim of this paper is to investigate the impact of lighting conditions on the detection accuracy of the vision-based equipment load detection approach. The work will be using artificial intelligence cameras to detect equipment information in different lighting levels, employing deep learning method to analyze and generate real-time equipment usage profiles for offices which can be inputted to the demand-based building controls to increase the efficiency of heating, ventilation, and air-conditioning systems. The performance of the developed approach in various illumination conditions was compared by using a building energy simulation tool. The results showed that as compared with the conventionally-scheduled heating, ventilation, and air-conditioning systems, the system with the use of equipment usage profiles conducted by the proposed approach can achieve up to 15% reduction in energy consumption depending on the setup of the camera in terms of indoor lighting levels. The finding indicates that adequate illumination level contributes to the decrease of building energy demand by achieving an effective deep learning approach.

Abstract

A two-dimensional gas-particle two-phase model has been developed based on Eulerian-Eulerian and Eulerian-Lagrangian approach. In this paper, the performance of the Diesel Particulate Filter (DPF) with a thin dense layer on the substrate wall of inlet channel is investigated by coupling microcosmic channel model with filtration model. The velocity field and filtration efficiency of the DPF with thin dense layer was studied and compared with that of the DPF without thin dense layer considering different space velocities, layer permeabilities and particle sizes. Besides, the dynamic of particle deposition inside the porous media of the DPF with layer was simulated by coupling the transient deep-bed filtration model with the DPF microcosmic channel model. The deposition mass distributions inside porous wall of particles with three different sizes were discussed. Results show that the existence of the thin dense layer can bring a much more uniform through-wall velocity along the inlet channel. The presence of the thin dense layer can raise the filtration efficiency of the DPF obviously, especially for particles with medium size. Meanwhile, affected by the existence of the thin dense layer, most particles are collected by the layer and the amount of particles penetrating into the porous wall decreases significantly. The penetration depth into the porous wall of 100 nm particles is much deeper than that of 10 nm and 1000 nm particles.

Abstract

In this paper, the thermodynamic analysis of three kinds of three-stage cascade refrigeration systems (TCRS) with internal heat exchanger (IHX) are studied using R1150/R170/R717 and R50/R170/R717, including TCRS with LTC IHX (TCRSIL), TCRS with MTC IHX (TCRSIM) and TCRS with IHXs in MTC and LTC (TCRSIL-M). The results indicate that when evaporation temperature is -120 oC ~ -80 oC and heat transfer efficiency of IHX is 60%, COP of TCRSs using R1150/R170/R717 is higher than that of TCRSs using R50/R170/R717. Under the same conditions, using IHX in TCRS will reduce the COP for R1150/R170/R717. Compared with TCRS without IHX, the average COP of TCRSIM, TCRSIL and TCRSIL-H decreased by 0.6%, 1.5% and 3.6% respectively. For R50/R170/R717, when evaporation temperature is -115 oC ~ -100 oC and heat transfer efficiency of IHX is 60%, using IHX in LTC is helpful to improve COP, but the increase is less than 1% compared with TCRS without IHX. However, in other temperature range, using IHX will reduce the COP. And the use of IHXs increases the exergy destruction of cascade heat exchangers in MTC and LTC. Therefore, R1150 /R170/R717 is recommended for TCRS, and IHXs are not recommended in TCRS.

Abstract

A comparative life-cycle greenhouse gas (GHG) emission analysis between a proposed integrated sewage sludge (SS) and food waste (FW) management strategy and business-as-usual scenarios in Singapore was performed in this study. The proposed approach was derived based on the design of co-located water reclamation plant and waste-to-energy incineration plant in Tuas, in which the SS and FW are anaerobic co-digested. The ratio of SS and FW was selected to be 1:1 for optimal biogas production. The effects of the power substitution and methane production rate uncertainties were investigated. The life-cycle GHG emission results show that the proposed strategy has a 64.3% reduction when compared to the current SS and FW treatments, or a 2129 tonnes CO2-eq reduction potential per year.

Abstract

In this paper, we present a novel approach developed through the TABEDE project to scale demand response across all building types. To this end, we propose an intelligent infrastructure that enables buildings to follow various demand-response schemes, that optimises the electricity consumption and generation of the buildings to reduce energy cost and promote RES penetration, and that is capable of connecting and controlling appliances seamlessly and in an interoperable manner. The approach is evaluated via a simulated district based on one of the project pilot sites in Cardiff, UK. The results show potential improvements to varying extents in solar PV self-consumption, energy cost reduction, and adhering to grid constraints.

Abstract

This work has studied the boiling heat transfer mechanism in a pump driven loop thermosyphon system. The coolant is Freon R134a which flows and boils in a tube with inside diameter of 8.05 mm. The results show that at a constant heat flux, the boiling heat transfer coefficient is not influenced by the coolant’s mass flow rate. In other ward, the boiling mechanism at this situation is the nucleate boiling instead of the convection boiling.

Abstract

To make efficient use of natural gas resource and realize carbon-free emission, a solar thermochemical energy storage system with the combined steam and dry methane reforming is proposed in this study. In the system, the methane reforming reaction is driven by concentrated solar energy, which upgrades solar thermal energy into chemical energy in the form of the syngas products. A reactor model that considers multiple reactions system and kinetic rate equations is used for the performance simulation of the thermochemical energy storage system. The results show that the distributions of temperature, mole fraction of components and conversion along reactor axis direction are uneven. The steam methane reforming reaction mainly consumes CH4 at the front part of the reactor, and the dry methane reforming reaction dominates the reaction system at the latter part of the reactor. The highest thermochemical energy storage efficiency can reach 61% under the condition of the stoichiometric feed ratio and 1 bar. The research findings provides an efficient and stable method for the reduction of natural gas consumption and the utilization of solar energy

Abstract

As a widely utilized phenomenon, condensation heat transfer is deeply related to the efficiency of energy utilization in industry. In recent decades, the condensation of vapor mixture attracted extensive attention, since the possibility to achieve high performance of heat transfer. During the condensation of some binary vapor Marangoni condensation), a special phenomenon was discovered that the spontaneous movement of condensate drop occurred. It was observed that condensate drops moved from the low temperature region to the high temperature region on a heat transfer surface. Therefore, the surface tension gradient induced by the temperature gradient was considered as the driving force. However, another affecting factor on the spontaneous movement of condensate drops, the direction of vapor flow, was also discovered. In this study, the experimental study was performed, and the results showed that the condensate drops tended to move towards the inlet direction of vapor flow.