The optimisation of intermittent heating for variable efficiency heating systems

The problem of minimising the heat input into an intermittently heated building can be transformed to a standard problem in mathematical programming. Previous limitations of this transformation to systems with constant efficiency are removed and the general formulation of the problem for a system with a monotonically varying efficiency is discussed. As an example of the technique, the optimal intermittent heating strategy for an electric heat pump with resistive heating booster is derived.     

应用LCC概念进行供热系统优化规划

应用寿命周期费用（ｌｉｆｅｃｙｃｌｅｃｏｓｔ）的概念和系统工程的方法,将热源,热网,热用户作为一个整体进行规划,使其技术和经济指标最佳,建立了以寿命周期费用最小为目标的供热系统优化规划数学模型,该模型用于大庆市供热工程中,效果很好。     

间歇供暖负荷计算方法研究

以夏热冬冷地区、寒冷地区和严寒地区典型城市的居住建筑和办公建筑为研究对象,分别采用DeST和DesignBuilder软件模拟分析了围护结构、换气次数及散热器和地板辐射两种供暖方式对间歇供暖热负荷的影响,给出了间歇供暖相对于连续供暖的供暖热负荷附加率,确定了合理的间歇供暖模式。结果显示,窗墙面积比对间歇供暖热负荷的影响可以忽略;换气次数每增加0.5h-1,间歇供暖热负荷附加率约增加5%;采用地板辐射供暖的间歇热负荷附加率比散热器供暖小3%～10%。     

热水间歇供暖加热过程数理模型

将建筑物供暖过程模拟划分为两个串联工作的热力系统,在假设条件下建立间歇供暖加热过程微分方程组及其关系式,并通过初步的实验加以验证,结果表明假设条件基本符合实际,误差能满足工程需要。     

Thermal capacity,intermittent heating and condensation

Based primarily on computer modelling, research by the UK Cement and Concrete Association has highlighted the importance of high thermal capacity of a house in maintaining higher temperatures during the ‘off’ period of normal intermittent space heating. These latter temperatures have a crucial bearing on the risks of condensation.     

关于间歇采暖室外计算温度的取值

基于暖通设计规范中采暖室外计算温度的统计方法,统计出各典型城市间歇采暖室外计算温度,并分析了相应的热负荷变化。结果表明:对于长期间歇采暖,室外计算温度的取值最大可高于现行规范值3.8℃;对于短期间歇采暖,最大可高于现行规范值4.6℃。以间歇采暖室外计算温度为依据,长期间歇和短期间歇采暖设计热负荷最大可分别降低9%和15%左右。     

Improvement of intermittent central heating system of university building

Most universities in Korea use intermittent central heating system which operates according to a preset intermittent schedule that is determined based on outdoor air temperature. This system is popular for university buildings due to its low initial cost and simple operation. But since it is not based on feedback control, the indoor thermal comfort is unsatisfactory. In this research, problem with the current control system is studied by experiment and dynamic simulation. The measurement shows that the indoor temperature rises to an uncomfortable range during heating and falls below comfortable range when heating is off. To solve this situation, an on-off control is implemented and simulated using a dynamic simulation program. Since there is a good agreement between experiment and dynamic simulation results, dynamic simulation is used to predict other results with different conditions of interest. The simulation shows that by implementing on-off control, the indoor space can be maintained within comfortable range, moreover using less energy. By reinforcing insulation to the walls that are exposed to the outdoor environment, heating energy can be saved further.     

住宅间歇供暖模拟分析

针对住宅间歇供暖方式的节能效果、设备容量、建筑保温形式和防冻等问题,采用全工况数值模拟方法,对北京市节能住宅间歇供暖特性进行了模拟分析。结果表明。在满足温度舒适的前提下,采用上班停暖的间歇供暖方式,全楼平均节能率不超过10％,且不会出现供暖房间水管冻坏问题;少数房间间歇供暖能耗比连续供暖能耗大;间歇供暖可使各房间最大热负荷增大25％～58％;内、外保温方式对间歇供暖能耗的影响较小。     

Dynamic simulation and parametric optimisation of a solar-assisted heating and cooling system

In this paper, a complete transient simulation model of a solar heating and cooling plant is presented. The system under analysis is based on the coupling of evacuated solar collectors with a single-stage LiBr-H₂O absorption chiller. An auxiliary heater, circulation pumps, storage tanks, feedback controller, mixers, diverters, ON/OFF hysteresis controller, single lumped capacitance building and controllers are also included.

The simulation was performed using the TRNSYS environment. This software also includes a detailed database with weather parameters for several cities all over the world. The system was simulated using specially designed control strategies and varying the main design variables. In particular, a variable speed pump on the solar collector was implemented, in order to maximise the tank temperature and minimise heat losses. A cost model was also developed in order to calculate operating and capital costs. A case study is presented and discussed, aiming at determining the performance of the system, from both energetic and economic viewpoints, in a specific application. A thermoeconomic objective function was also introduced, and finally a sensitivity analysis was performed, in order to calculate the set of synthesis/design parameters that maximise the global efficiency of the system or the above-mentioned objective function, for the case under analysis. The results of the case study showed that a good selection of the solar collector (SC) area and of the volume of the storage tank (TK1) are mandatory. The Primary Energy Saving (PES) is positive in the case of high solar field area, while the optimal thermo-economic volume of the storage tank was found to be 75 l/m². The parametric optimisation also showed that it is important to lower the SC and auxiliary heater (AH) set-point temperatures, as much as possible.     

西安某小区供热系统间歇运行供暖房间热环境分析

对西安市某小区集中供热系统间歇调节运行的室内热环境进行了动态实测分析,得出供水温度的变化规律及供暖房间热舒适的现况.指出只要适当调整供热时间就能明显地改善热舒适条件.     

The optimisation of cold rolled formed products

The design, development and analysis of a new cold roll formed product is presented. The objective of this exercise is to produce an economic and efficient profile which incorporates the basic C shape, with additional enhancements to improve its structural performance. A new sectional properties computer program was employed to analyse the profile. The potential of this software is also explored. Since it is able to determine the sectional properties of an arbitrary shape, it is a powerful tool in the optimisation of new cold rolled formed products.     

城市集中供热无人值守热力站的建设

结合太原市瑞光热电联产供热工程的实际应用情况,就无人值守热力站的组织架构及控制模式进行了介绍,指出通过无人值守热力站的建设,能够优化热力站的运行控制策略,节能降耗,取得了良好的社会和经济效益。     

The application of direct search optimisation to structural design

Development of an optimisation method suited to structural engineering design applications is described briefly. The method is essentially a conventional direct-search technique with exterior penalty constraints but uses variable penalty factors during the search to improve mobility between feasible regions. The method is illustrated by application to design of a composite box-girder footbridge, employing eight design variables and nineteen constraints, and the results are used to demonstrate the importance of considering sub-optima as well as the global optimum. The usefulness of univariant parameter/cost relationships in the region of global and local optimum points, derived as an intrinsic part of the optimisation process, is also stressed.     

城市集中供热方式的探讨

城市集中供热方式可分为热电厂集中供热系统、锅炉房集中供热系统、混合系统。热电厂的突出特点是热电合产,使能源的有效利用程度提高,从而能节约燃料。但受诸多因素制约。集中锅炉房节能效果较热电厂差,但热电厂种种制约条件致使其不可能全部替代集中锅炉房,二者长期共存将起到取长补短的作用。应广泛探索提高集中供热经济性途径,使城市集中供热在节能工作中发挥应有的作用。     

The Warsaw district heating system

In Warsaw, Poland, the capacity of the heat-generating power plants in 1982 was 4352 MW and the length of the network was 1187 km. This paper describes the development of this district heating system over the last 30 years. Figures show cross-sections of main ducts and tunnels.     

散热器对流采暖与地板辐射采暖的比较分析

对散热器对流采暖与地板辐射采暖的散热机理、室内温度的垂直分布、对室内风速分布的影响以及对建筑节能的作用等进行了分析,指出了地板辐射采暖优于传统散热器对流采暖。     

The effect of intermittent chlorination on freshwater phytoplankton

Lake Michigan phytoplankton showed a significant loss of chlorophyll a and permanent reduction of carbon uptake rates after exposure for 30 min to concentrations of total residual chlorine at or above 1 mg l⁻¹. At this level the photosynthetic system of the algae was irreversibly destroyed. Below 0.1 mgl⁻¹ total residual chlorine only slight changes in chlorophyll a were noted, and, following an initial decrease, carbon uptake rates exhibited nearly complete recovery after 24 h.     

供热换热站及热力二次网节能改造浅析

以某热力站及热力二次网节能改造工程为背景,以解决用户冷热不均和降低能耗为目的,主要采取更换高效循环泵和二网平衡节能措施,不仅解决了用户冷热不均的问题,而且有效的降低了能耗。节能改造后节电率57. 23%,节热率12. 57%,节能效果显著。     

供热系统的动态调节

考虑供热系统设备和建筑物的热惰性对系统热力工况的影响,提出采用动态调节进行运行调节,并给出了预测运行参数的模型。