Achieving high power heat-recovery systems using molecularly-complex fluids

要实现英国和欧盟的排放目标，就需要对发电和制造业进行转型。在英国，我们每年消耗350千瓦时的电力，但现代发电站的效率通常在50%左右，很大一部分能源被浪费为废热。只要回收10%的热量，就能节省相当于22个发电站的发电量。这还不包括可以从制造业中回收的热量，在制造业中，金属成型过程中的加热和冷却浪费了大量的能量。为了使热回收在经济上可行，低温有机朗肯循环（ORC）可以使用沸点接近环境温度的流体，例如许多“分子复杂”流体。能量在一个穿过涡轮机的ORC中被提取，在那里这些“分子复杂”的流体以气态存在，并以高速通过涡轮机。增加从涡轮机中提取的功率使热回收系统更加经济实惠，并且可以通过提高整个涡轮机的压力比来实现。为了有效地做到这一点，需要更好地理解分子复杂的气体流动，因为我们对涡轮机中这些复杂的流动知之甚少。在ORC涡轮机的分子复杂的气体动力学缺乏深入的了解意味着它是不太可能的最佳功率水平正在实现与目前的设计方法。因此，本提案旨在确定通过利用有机朗肯循环涡轮机中分子复杂性的影响来显着增加热回收系统功率输出的方法。目标是将目前的涡轮功率水平提高一倍。为了确定实现这一目标的方法，计划进行实验和计算测试的结合。分子复杂气体流动的实验将使用专门设计的实验试验台进行研究，该试验台将能够模拟ORC涡轮机中的流动条件。计算模拟将涉及使用一个研究流动求解器，它将被修改以考虑分子复杂气体的性质。实验数据将有助于开发精确的计算模型，该模型将用于确定在高压比下运行的新型涡轮叶片设计。这项研究将直接造福于流体力学研究界和发电行业。这项研究将提高我们对分子复杂流体的流体力学的基本理解，也将有助于可持续发电技术的发展。对涡轮机中分子复杂气体流动的更好理解有可能大大减少英国对化石燃料的依赖，并提高我们从发电站和制造过程以及太阳能和地热辐射中回收目前“浪费”的热量的能力。这在帮助应对气候变化和改善英国能源安全方面都有很大的社会效益。这项工作将有助于实现《2008年英国气候变化法案》的目标，即在1990年的基础上，到2020年减少34%的温室气体排放，到2050年减少80%。

Achieving UK and EU emissions targets requires a transformation in the power generation and manufacturing industries. In the UK we consume 350TWhr of electricity every year, but with modern power-stations which are typically around 50% efficient a large proportion of energy is wasted as rejected heat. Recovering just 10% of this heat would save the equivalent power output of 22 power stations. This is not to mention the heat which could be recovered from manufacturing industries where large quantities of energy are wasted through the heating and cooling during metal-forming processes. In order to make heat-recovery economically viable, low-temperature Organic Rankine Cycles (ORC) can be deployed using fluids with boiling-points close to ambient temperatures, such as many 'molecularly-complex' fluids. The power is extracted in an ORC across a turbine, where these 'molecularly-complex' fluids exist in a gaseous state, and pass through the turbine at high speeds. Increasing the power extracted from the turbine makes heat-recovery systems much more economically favourable and can be achieved by raising the pressure ratio across the turbine. In order to do this efficiently requires a better understanding of molecular-complex gas flows because there is very little known about these complex flows in turbines. The lack of an in-depth understanding of the molecular complex gas-dynamics in ORC turbines means that it is unlikely that optimum power levels are being achieved with present-day design methods.Therefore this proposal aims to determine methods of significantly increasing heat-recovery system power outputs by exploiting the effects of molecular complexity in Organic Rankine Cycle turbines. A target is set of doubling current turbine power levels. In order to determine methodologies to achieve this, a combination of experimental and computational tests are planned. Experiments of molecularly complex gas flows will be studied using a specially designed experimental test-rig which will be able to mimic the flow conditions found in the ORC turbine. The computational simulations will involve the use of a research flow-solver, which will be modified to account for molecular-complex gas properties. The experimental data will aid the development of an accurate computational model, which will then be used to determine novel turbine blade designs to operate at high pressure ratios.This research will directly benefit both the fluid-mechanics research community and the power-generation industry. The research will improve our fundamental understanding of the fluid mechanics of molecularly complex fluids, and will also aid the development of sustainable power generation technologies. An improved understanding of molecular-complex gas flows in turbines has the potential to substantially reduce the UK's fossil fuel dependence and improve our ability to recover currently otherwise 'wasted' heat from power stations and manufacturing processes as well as solar and geothermal radiation. This has a large societal benefit both in-terms of aiding the fight against climate-change and improving the UK's energy security. This work will help towards meeting the targets of the UK Climate Change Act 2008 to reduce by 34 percent our greenhouse gas emissions by 2020 and 80 percent by 2050, against the 1990 baseline.