基于太阳能利用的溴化锂—水变效吸收式制冷的循环与系统研究

发布时间：2018-03-24 08:55

本文选题：太阳能制冷　切入点：吸收式制冷　出处：《上海交通大学》2015年博士论文

【摘要】：太阳能吸收式制冷是一项环保节能的制冷技术,是太阳能制冷的重要研究方向。太阳能吸收式制冷系统主要由太阳能集热器和制冷机组成,大部分使用溴化锂-水吸收式制冷机作为冷量输出单元。其中太阳能集热器提供热源的温度会随着时间的变化而变化,并只能在晴天提供热源,具有不稳定性和间隙性。吸收式制冷机则需要温度稳定的热源,机组COP随热源温度变化不大,所以吸收式制冷机与太阳能集热器的组合存在一些不匹配问题。本文从能量流动角度分析了这些不匹配问题,主要有太阳能间隙性带来的需要额外热源输入问题,和太阳能不稳定性带来的能源品位浪费问题。针对这两个问题本文进行了以下研究并得出相关结论:(1)由于太阳能具有间隙性,太阳能吸收式制冷系统大多需要和化石燃料互补以确保系统连续运行。由于化石燃料燃烧所得能量品位高,采用单效溴化锂-水吸收式制冷机为冷量输出单元的系统在使用额外热源时,存在很大的能源品位浪费。这种品位浪费可以通过采用单/双效吸收式制冷机来解决,即系统在太阳能驱动下以单效吸收式制冷模式运行,在燃气驱动下以双效吸收式制冷模式运行。本文对一个太阳能/燃气驱动单/双效吸收式供能系统进行了实地运行分析,得到了系统一整年的运行情况。系统的两种模式均可以稳定运行,太阳能驱动模式可以达到0.62的COP,相比纯燃气驱动系统整年燃气消耗量减少50.3%。(2)针对低温太阳能热源的不稳定性,提出使用低温太阳能变效(0.n效)吸收式制冷循环。该吸收制冷循环是在半效循环的基础上将内部换热结构改为外部换热结构而得到,通过改变中压蒸发器冷量分流比例可以得到从半效到单效的变效制冷。基于模型对该制冷方式进行了计算,在蒸发温度5oC,冷却水温分别为32oC和40oC的工况下,循环可工作热源范围分别为83.5oC-110oC和104oC-127oC,相比单效循环先比工作温度范围分别扩大了2倍和6倍,而COP则在0.3到0.7之间变动。(3)针对中温太阳能热源的不稳定性,提出使用具有更高经济性的中温太阳能变效(1.n效)吸收式制冷循环。为了得到1.n效吸收式制冷循环,对吸收式制冷循环进行了理论分析和构建方式分析,将循环构建方式主要归纳为溶液回路外的热质耦合和溶液回路内的热质耦合。传统循环对热源适应性差是因为这些循环采用回路外耦合构成,循环被这些耦合锁死所以在热源温度变化时无法做出相应改变。通过分析得到吸收循环构建的几个基本准则。针对中温太阳能利用,依据这些准则对1.5效系统进行基于回路外耦合的构建,得到8种新型1.5效吸收式制冷循环形式。再通过浓度变化延展增加回路内耦合过程,提高循环自由度,得出另外4种循环方式。其中一种即为所需要的中温变效(1.n效)循环。(4)对以溴化锂-水为工质的中温变效(1.n效)循环进行理论分析。循环将高压发生器产生蒸汽分为两部分,一部分进入冷凝器,一部分进入高压吸收器。进入高压吸收器的蒸汽降低了溶液浓度和平衡温度,此时即便高压冷凝热温度没有双效循环高,也可以驱动溶液的发生过程,从而达到了对高压冷凝热的回收。根据发生温度不同,可以通过调整进入高压吸收器溶液流量来改变循环。通过建模计算,在85 oC到150 oC之间的发生温度下,循环可以得到0.75到1.08的COP。(5)基于1.n效循环对1.n效溴冷机进行设计和实验分析。通过计算,确定发生温度125oC、冷凝温度40 oC、吸收温度35 oC和蒸发温度5 oC的设计工况。对所加工的50kW机组测试得到机组可以在95 oC到120 oC的发生温度工况下得到0.69到1.08的COP。根据实验数据和理论计算数据的对比可以得知,实验COP和相应工况下理论计算COP的平均误差为7.3%。(6)基于实验数据得到了1.n效溴冷机的人工神经网络模型。模型以热源进口温度、冷却水进口温度、冷水进口温度和所需冷量为输入参数,以冷水出口温度和冷却水出口温度为输出参数。基于TRNSYS平台建立CPC集热器和1.n效溴冷机的模块,并组建CPC驱动1.n效溴冷机的系统,并进行模拟计算,对系统进行优化计算。得到该太阳能制冷系统的制冷机在运行中可以达到1.1的瞬时COP和超过0.8的平均COP。
[Abstract]:Solar absorption refrigeration refrigeration technology is a green energy, is an important research direction of the solar refrigeration. Mainly by the solar collector and refrigerator solar absorption refrigeration system, most of the use of LiBr-H2O as cooling output unit. The solar collector and the temperature of the heat source will provide change over time, and can provide heat in sunny days, with instability and gap. Absorption refrigerating machine requires heat source temperature stable, little change in unit COP with heat source temperature, so the combination of absorption chiller and solar collector has some matching problem. This paper analyzes these problems do not match from the angle of energy flow, mainly caused the need for additional clearance solar heat source, the problem of energy waste and solar grade bring instability to the. Two problems this paper carried out the following research and draw relevant conclusions: (1) because the solar energy is intermittent, solar absorption refrigeration system mostly fossil fuels and complementary systems to ensure the continuous operation. Due to the burning of fossil fuels the energy of high grade, the single effect lithium bromide - water absorption chiller for cooling output unit in the use of additional heat source, there is a big waste of energy grade. The waste grade can be achieved by the use of single / double effect absorption refrigerating machine to solve, namely system driven by solar energy on the single effect absorption refrigeration mode operation in gas driven by double effect absorption refrigeration operation mode. In this paper a solar / gas driven single / double effect absorption type energy supply system for field operation analysis, get the operation situation of the system for a whole year. Two modes of system can be stable operation, solar energy The driving mode can reach 0.62 COP, compared with the pure gas drive system year gas consumption reduced 50.3%. (2) for low temperature solar heat instability, put forward using low temperature solar effect (0.n effect) absorption refrigeration cycle. The absorption refrigeration cycle is based on internal circulation half effect heat exchanger structure will change the structure of external obtained by changing the medium pressure evaporator cooling capacity shunt ratio can be obtained from the half effect to effect refrigeration. The single effect model to calculate the refrigeration mode based on 5oC in evaporation temperature, cooling water temperature are respectively 32oC and 40oC under the condition of circular working range of heat sources were 83.5oC-110oC and 104oC-127oC. Compared with the single effect cycle than the first temperature range were expanded by 2 times and 6 times, while COP changes between 0.3 to 0.7. (3) according to the temperature of the solar heat instability makes has higher Temperature of the solar economy variable effect (1.n effect) absorption refrigeration cycle. In order to get the 1.n effect absorption refrigeration cycle, the absorption refrigeration cycle are analyzed by theoretical analysis and construction methods, construction methods are summarized for the circulating heat coupling solution loop heat and mass coupling and loop. The traditional solution cycle of heat adaptability is because these cycles with loop coupling, the coupling loop is locked so in the heat when the temperature changes to make the corresponding change. Through the analysis of several basic principles of circular construction to be absorbed. According to the temperature of the solar utilization, on the basis of the criterion of 1.5 effect system construction based on loop coupling. Get 8 new 1.5 effect absorption refrigeration cycle. To increase the coupling process of the loop through the change of the concentration extension, improve circulation degree of freedom, the other 4 cycles. A temperature change is in effect required (1.n effect) cycle. (4) for lithium bromide - water as refrigerant temperature variable effect (1.n effect) cycle were analyzed. The loop will produce steam high pressure generator is divided into two parts, one part enters the condenser part in high pressure absorption. The steam into the high-pressure absorber reduces the solution concentration and the equilibrium temperature, even if high-pressure condensation heat temperature without double cycle high, can also occur process driven solution, so as to achieve the recovery of high pressure condensing heat. According to the different temperature, can adjust the flow to change into a high-pressure absorber solution by modeling cycle. In the calculation, 85 oC to 150 oC between the temperature, cycle can get 0.75 to 1.08 COP. (5) 1.n effect cycle design and experimental analysis on 1.n effect based on lithium bromide refrigerator. Through calculation, the temperature of the condensing temperature 125oC, 4 0 oC, 35 oC design condition absorption temperature and evaporation temperature of 5 oC. The test of 50kW units are set in the processing of 95 oC to 0.69 to 1.08 COP. according to the experimental data and the theoretical calculations of the contrast can be learned the cause of temperature of 120 oC, the average error calculation of COP COP and the corresponding experimental conditions under the theory of 7.3%. (6) based on the experimental data obtained by the artificial neural network model 1.n. Effect of lithium bromide refrigerator to the heat source inlet temperature model, inlet temperature of cooling water, cooling water inlet temperature and required cooling capacity as input parameters, the cold water outlet temperature and the cooling water outlet temperature as output parameters. TRNSYS platform based CPC set heat exchanger and 1.n effect LiBr absorption chiller module based on the system and the formation of CPC driven 1.n effect LiBr absorption chiller, and simulated, to optimize the system. The calculation of refrigeration machine solar cooling system in the operation can be Up to 1.1 of the instantaneous COP and an average of more than 0.8 of the COP.

【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB657

【相似文献】