Numerical Investigation on Energy Efficiency of Heat Pump with Tunnel Lining Ground Heat Exchangers under Building Cooling

For mountain tunnels, ground heat exchangers can be integrated into the tunnel lining to extract geothermal energy for building heating and cooling via a heat pump. In recent decades, many researchers only focused on the thermal performance of tunnel lining GHEs, ignoring the energy efficiency of the heat pump. A numerical model combining the tunnel lining GHEs and heat pump was established to investigate the energy efficiency of the heat pump. The inlet temperature of an absorber pipe was coupled with the cooling load of GHEs in the numerical model, and the numerical results were calibrated using the in situ test data. The energy efficiency ratio (EER) of the heat pump was calculated based on the correlation of the outlet temperature and EER. The heat pump energy efficiencies under different pipe layout types, pipe pitches and pipe lengths were evaluated. The coupling effect of ventilation and groundwater flow on the energy efficiency of heat pump was investigated. The results demonstrate that (i) the absorber pipes arranged along the axial direction of the tunnel have a greater EER than those arranged along the cross direction; (ii) the EER increases exponentially with increasing absorber pipe pitch and length (the influence of the pipe pitch and length on the growth rate of EER fades gradually as wind speed and groundwater flow rate increase); (iii) the influence of groundwater conditions on the energy efficiency of heat pumps is more obvious compared with ventilation conditions. Moreover, abundant groundwater may lead to a negative effect of ventilation on the heat pump energy efficiency. Hence, the coupling effect of ventilation and groundwater flow needs to be considered for the tunnel lining GHEs design.

Energy Optimization of the Pumping Station

The main challenge in the field of water distribution systems (WDS) is (re)designing the network in order to achieve savings. In many water systems, there are pumping stations designed for much larger flows than what would be observed under normal operating conditions. On the other hand, reducing the diameter of the water pipes has become the main saving method. Designers very often forget to design the network so that it can be used for fire protection purposes. The computer modelling of water networks supports the decision-making process by identifying the optimal compromise between cost and performance (e.g., flow, velocity, pressure). Computer models help in the selection of optimal values of hydraulic pumps, preparation of the pump control method and selection of energy-optimized pumping systems, ensuring the efficiency and pressure of the WDS during normal operation and in fire conditions. The article presents the results of optimization of the pump station in terms of efficiency and pressure in the system, and optimization of pump energy consumption. Computer simulations of the water supply system, measurements of pressure and flow, hydrant flow tests, and model calibration were used in the research.

Evaluation the effect of the ambient temperature on the liquid petroleum gas transportation pipeline

Liquefied petroleum gas (LPG) plays a major role in worldwide energy consumption as a clean source of energy with low greenhouse gases emission. LPG transportation is exhibited through networks of pipelines, maritime, and tracks. LPG transmission using pipeline is environmentally friendly owing to the low greenhouse gases emission and low energy requirements. This work is a comprehensive evaluation of transportation petroleum gas in liquid state and compressible liquid state concerning LPG density, temperature and pressure, flow velocity, and pump energy consumption under the impact of different ambient temperatures. Inevitably, the pipeline surface exchanges heat between LPG and surrounding soil owing to the temperature difference and change in elevation. To prevent phase change, it is important to pay attention for several parameters such as ambient temperature, thermal conductivity of pipeline materials, soil type, and change in elevation for safe, reliable, and economic transportation. Transporting LPG at high pressure requests smaller pipeline size and consumes less energy for pumps due to its higher density. Also, LPG transportation under moderate or low pressure is more likely exposed to phase change, thus more thermal insulation and pressure boosting stations required to maintain the phase envelope. The models developed in this work aim to advance the existing knowledge and serve as a guide for efficient design by underling the importance of the mentioned parameters.

Nature-Inspired Structures Applied in Heat Transfer Enhancement and Drag Reduction

Heat exchangers are general equipment for energy exchange in the industrial field. Enhancing the heat transfer of a heat exchanger with low pump energy consumption is beneficial to the maximum utilization of energy. The optimization design for enhanced heat transfer structure is an effective method to improve the heat transfer coefficient. Present research shows that the biomimetic structures applied in different equipment could enhance heat transfer and reduce flow resistance significantly. Firstly, six biomimetic structures including the fractal-tree-like structure, conical column structure, hybrid wetting structure, scale structure, concave-convex structure and superhydrophobic micro-nano structure were summarized in this paper. The biomimetic structure characteristics and heat transfer enhancement and drag reduction mechanisms were analyzed. Secondly, four processing methods including photolithography, nanoimprinting, femtosecond laser processing and 3D printing were introduced as the reference of biomimetic structure machining. Finally, according to the systemic summary of the research review, the prospect of biomimetic heat transfer structure optimization was proposed.

One-dimensional planar topological laser

Topological interface states are formed when two photonic crystals with overlapping band gaps are brought into contact. In this work, we show a planar binary structure with such an interface state in the visible spectral region. Furthermore, we incorporate a thin layer of an active organic material into the structure, providing gain under optical excitation. We observe a transition from fluorescence to lasing under sufficiently strong pump energy density. These results are the first realization of a planar topological laser, based on a topological interface state instead of a cavity like most of other laser devices. We show that the topological nature of the resonance leads to a so-called “topological protection”, i.e. stability against layer thickness variations as long as inversion symmetry is preserved: even for large changes in thickness of layers next to the interface, the resonant state remains relatively stable, enabling design flexibility superior to conventional planar microcavity devices.

Development and Verification of an Integrated Seawater Desalination and Renewable Energy System Model

This work investigates the modeling and verification of seawater reverse osmosis powered by renewable energy resources (SWRO-RES). The model includes one stage of RO membranes, high pressure (HP) pump, energy recovery devices (ERD), Wind turbines (WT), photovoltaic panels (PV), and electrical grid as a back-up for the cases when there is weak penetration of the RES. Antibugging and tracing for the computer model were used as part of the code verification to discover all coding errors and check whether the computer model conforms to the SWRO specifications. After that, the calculations verifications process was performed using sensitivity analysis (SA) to evaluate whether the model response follows the anticipated direction and to check the model at some extreme conditions. Four SA cases were implemented to evaluate the SWRO-RES freshwater production, freshwater concentration, recovery rate, and specific energy consumption (SEC). Case 1 was the SA for different feed pressure values. In this case, it is important to find the pressure value that gives the lowest freshwater concentration. Case 2 was the SA for different feedwater temperature values. While case 3 was the SA for the feedwater concentration. In all these cases, the model shows a verified response and as anticipated. The last SA case was to study the effect of different numbers of WT and PV panels and evaluate the electrical grid share considering one year of operation for the SWRO-RES plant.

Analysis of an Integrated Thermal Energy System for Applications in Cold Regions

This paper performed analyses on a proposed direct wind-powered heat pump integrated with a pond which serves as an evaporator for space heating in cold regions. The analysis was conducted using environmental data for selected locations in Canada and the Engineering Equation Solver. Three different pairings of heat pumps and wind turbines were studied (a wind-powered heat pump with a pond as an evaporator, a wind-powered heat pump without a pond, and an electricity-powered heat pump). Energy and exergy analyses were performed on the systems. The novelty in the present study is in the use of a wind turbine to directly power the heat pump and using a pond as the evaporator. The results show that the proposed system has the highest coefficient of performance compared to the others. The average coefficient of performance for the selected locations is 2.7, which is at least 67% better than the others. Similarly, the overall exergy for the proposed system is 16.9%, which is at least 40% better than the others. The average heating capacity of the selected locations for the proposed system is 4.5 kW, which is from 29% to 300% better than the others. Additionally, the sustainability index for the proposed system is the highest for the proposed system. The results have shown that the proposed system has superior overall performance for space heating in cold regions.

Near and mid-infrared optical vortex parametric oscillator based on KTA

We investigated high energy, near and mid-infrared optical vortex lasers formed by a 1 μm optical vortex-pumped KTiOAsO4 (KTA) optical parametric oscillator. The orbital angular momentum (OAM) of the pump beam can be selectively transferred to the signal or idler output by changing the reflectivity of the output coupler. With this system, 1.535 µm vortex signal output with an energy of 2.04 mJ and 3.468 µm vortex idler output with an energy of 1.75 mJ were obtained with a maximum pump energy of 21 mJ, corresponding to slope efficiencies of 14% and 10%, respectively. The spectral bandwidth (full width at half maximum, FWHM) of the signal and idler vortex outputs were measured to be Δλs ~ 1.3 nm (~ 5.5 cm−1) and Δλi ~ 1.7 nm (~ 1.4 cm−1), respectively.