Search

This paper presents a new technology based on a direct-fired absorption heat pump and a direct-contact total heat exchanger. An analysis of existing techniques for heat recovery shows that the limi...

Beach wells are designed for pumping seawater in the seawater-source heat pump (SWHP) system with low-energy consumption. However, the multi-wells SWHP system is a complex system that has multi-objectives (energy consumption and lifetime cost) and multi-factors (land width and length, the arrangement of beach wells, permeability, and specific heat capacity of rock-soil). The system optimization assignment becomes a formidable work due to the increased number of beach wells with increasing energy system scale, and this paper aims to study the system optimization method to meet the energy-saving requirements of building engineering. A stepwise enumeration optimization method is developed for efficient optimization of the multi-wells SWHP system. Based on the established mathematical models, the numerical simulation method is used in the optimization procedure . A case study is conducted, the optimization parameters are obtained: 1260 J/(kg·°C) and 0.0007 m/s of physical parameters, 750 m width and 500 m length of land size, one row and three columns of beach wells, the research result indicates that a greater land size and a greater number of beach wells is not the optimal solution. The proposed stepwise enumeration method provides higher precision and better analyticity than the orthogonal method. Also, the optimization speed is improved compared to the enumeration method. Enumeration requires 5 6 calculation times, while the stepwise enumeration method needs only 100 calculation times. As such, the proposed method is feasible and effective in optimizing the multi-wells SWHP system, and the corresponding optimization results can scientifically guide system design.

A new type of air-conditioning terminal device that could be used both for cooling in summer and heating in winter was studied in the research. In order to obtain the heat transfer characteristics of the device, a test rig was set up and measured, and then the cooling capacity and the percentage of radiation heat exchange of the device were calculated and analyzed. The results show that the total cooling capacity of the device can reach 631.0 W (i.e., 143.8 W/m2) under the supply water temperature of 8°C and the water flow rate of 240 L/h. The proportion of the radiation heat exchange rate to the total heat exchange rate is around one-third. The cooling capacity comparison between the device and the radiant cooling ceiling shows that the cooling capacity of the device increases by about 57.6% per square meter surface area over the value of the radiant cooling ceilings at the same inlet cooling medium temperature. In the end, the differences between this radiant–convective air-conditioning terminal device ...

Optimization of the district heating (DH) piping network is of vital importance to the economics of the whole DH system. The application of distributed variable frequency speed pump (DVFSP) in the district heating network has been considered as a technology improvement that has a potential in saving energy compared to the conventional central circulating pump (CCCP) district heating system (DHS). Economic frictional factor is a common design parameter used in DH pipe network design. In this paper, the mathematical model of economic frictional factor based on DVFSP DHS is established, and influence factors are analyzed, providing a reference for engineering designs for the system. According to the analysis results, it is studied that the energy efficiency in the DH system with the DVFSP is compared with the one in the DH system with conventional central circulating pump (CCCP) using a case based on a district heating network in Dalian, China. The results of the study on the case show that the average electrical energy saved is 49.41% of the one saved by the DH system with conventional central circulating pump in the primary network.

Building space heating and cooling system built-in the town's infrastructure is an important factors for building energy consumption and carbon emission source. In order to understand the roles of building energy system in the global warming, this paper established a mathematical model of energy consumption and carbon emission for the building energy system. Two district heating systems for residential buildings and nine space heating and cooling systems for public buildings were selected to analyze their energy consumption, carbon emission and economy based on a calculating model. The results showed that the two residential building cases B01 and B02 of life-cycle carbon emissions are 743.60 kg/m2 and 620.98 kg/m2, the public building cases B03∼bl1 of life-cycle carbon emissions are 800.15–1377.85 kg/m2. Equipment materials production, installation and maintenance phase embodied energy and carbon emissions proportion reached up to 6%∼14%, energy conservation and emissions reduction potential should not be neglected. The application of some renewable energy reaches a certain effect of energy conservation and emissions reduction in building, but the life cycle cost of emission reduction is much higher than carbon tax in China.

The thermal energy storage (TES) technology is an effective method to enhance the planning and the economy of the combined heat and power (CHP) plants, while it has still not been broadly promoted in China. In this paper we firstly establish a mathematical model for a Chinese CHP plant with TES. Then the EnergyPRO software is used to find the optimum type of the TES tank in a three-tariff electricity pricing market and the operation strategy of the CHP plant with the selected TES tank is studied. Thirdly, the economic benefits of the system with/without TES is evaluated. The results show that adding a TES tank with volume of 24000m3 can significantly increase operational profits of the CHP system and reduce the use of peak-shaving heat source.

The electric-driven seawater source heat pump district heating system is a renewable energy utilization system, but this cannot guarantee the energy-saving effect of the system. The static energy-saving judgment between this system and the conventional boiler house district heating system was provided in a former research paper. However the static method has proved to be a very rough evaluation method and may lead to misjudgment as well. So a quasi-dynamic method, taking the total energy consumption during a whole heating season into consideration, is established in this paper. The energy-saving index turns out to be the expression of the lower limit of the average COP of the seawater source heat pump unit throughout the heating season (COPh,mc). Then a case study is presented to show how the index of COPh,mc and the actual average COP of the heat pump unit throughout the heating season (COPh,ma) are calculated. The calculation results show that the quasi-dynamic method improves the calculation accuracy dramatically, and thus provides a better solution to the quantitative energy-saving evaluation of the electric-driven seawater source heat pump district heating system.

This paper presents a study on the utilization of ocean thermal energy in Dalian. Coastal areas are ideal sites for the application of seawater-source heat pump technology (SWHP) to provide district cooling and heating. The technical requirements and the scheme design in the context of marine climate are discussed. A government-commissioned feasibility study of a proposed district energy site in Dalian, with an estimated 68 MW heating load and 76 MW cooling load plant capacity is then described. The economic, energy and environmental impacts are analyzed. In order to get a better understanding of economic justification and benefits of two different systems, annual cost (AC) and net present value (NPV), are used. A series of sensitivity analyses are undertaken to investigate the magnitude of the effect of the parameters variation on cost calculation. The numerical simulations of seawater temperature field are performed by using a two-dimensional convection–diffusion equation model to evaluate environmental impacts. Study indicates that Dalian has great potential for applying SWHP system. It is both technically and economically feasible because of the favorable geographical location and urban environment.

The seawater-source heat pump district heating system (SSHPDHS) is a renewable energy utilization system. However, under what conditions can the system achieve its energy-saving effect and how to evaluate its energy-saving potential are not very clear in practice, yet they are of vital importance for the popularization of the system in the cold coastal area. The paper derived an expression of the critical COP value of the heat pump unit for energy-saving (COPh,c) through the comparison of the SSHPDHS and the conventional boiler-house district heating system (BHDHS) in energy consumption aspect. At the same time, the actual COP values of a heat pump unit (COPh,a) under different evaporator water temperatures are calculated out by an experiment data regression model on the basis of the manufacturer’s dataset. Then the comparison of COPh,c and COPh,a under several typical scenarios are presented, which make the energy-saving judgement of an SSHPDHS and its energy-saving potential readily available. It concludes that the utilization of renewable energy of the SSHPDHS cannot guarantee its energy-saving effect due to the restriction of the actual COP value of a heat pump unit. It is also found that both the natural conditions of the seawater and the heating district radius (RH) are the most important factors that affect the energy-saving potential of the SSHPDHS.