The microchannel heat exchanger is one of the most compact and effective heat exchangers used for cooling devices in building air conditioning system, while application of nanofluids in microchannel further enhance its thermal performance due to its much higher thermal conductivity. Considering the continuous rapid increase in energy consumption in the building sector, especially in air conditioning systems, the heat transfer performance of a microchannel with nanofluids should be further enhanced to realize energy savings. This study analyzes the influence of combining nanofluid and flow disturbance structure on the heat transfer enhancement of a microchannel, which is also the noted novelty. A rectangular grooved microchannel (RGMC) is proposed, and its thermal performance using Al2O3/water nanofluids is investigated using the CFD method, with the mixture model to simulate the Al2O3/water nanofluids considering the slip velocity between the base fluid and nanoparticles. The results show that at 1.5 m/s, Nu of RGMC with 2 vol% nanofluids is 38.5% larger than that of smooth microchannel (SMC) with the same nanofluids, and 36.7% larger than that of RGMC with pure water, indicating the much better heat transfer performance of the novel designed RGMC structure. The maximum temperature for RGMC is 5 K lower than SMC with 2 vol% Al2O3/water nanofluid at inlet velocity of 1.5 m/s. Further analysis on the integrated effect between fluid flow and heat transfer shows that the synergy angle β near the center line of RGMC is much lower than that of SMC, representing that the better thermal performance is caused by the flow structured induced by the grooves. Moreover, at 1.5 m/s, βα of SMC with 2 vol% nanofluid is 89.4 Deg, which is 1.66 Deg higher than the βα value of RGMC, while at 0.25 m/s, the βα of two types of microchannel are close to each other. This indicates that the groove structure shows greater enhancement at higher inlet velocity. It is concluded that combining nanofluid and groove structure can significantly enhance heat transfer of the microchannel. The nanofluid enhances heat transfer at lower inlet velocity, while the groove structure enhances it at higher inlet velocity. This study will be helpful for the design of a high-efficiency microchannel heat exchanger that promotes building energy savings.

There are always arguments about the unadorned language and the nature in Wordsworth’s poems. Some consider it as a sentimental approach to escape from the reality, while others are on the contrary. This article is going to check how the language was used, and in what aspect Wordsworth chose to depict the nature to find relationship between human and nature, as well as the society. By examining the paradoxes in the poetry, the article will explore how Wordsworth made innovation at his time, which added a new angle to perceive the world.

With the application of microdevices in the building engineering, aerospace industry, electronic devices, nuclear energy, and so on, the dissipation of high heat flux has become an urgent problem to be solved. Microchannel heat sinks have become an effective means of thermal management for microdevices and enhancements for equipment due to their higher heat transfer and small scale. However, because of the increasing requirements of microdevices for thermal load and temperature control and energy savings, high efficiency heat exchangers, especially microchannels are receiving more and more attention. To further improve the performance of microchannels, optimizing the channel geometry has become a very important passive technology to effectively enhance the heat transfer of the microchannel heat sink. Therefore, in this paper, the microchannel geometry characteristics of previous studies are reviewed, classified and summarized. The review is mainly focused on microchannel geometry features and structural design to strengthen the effect of heat transfer and pressure drop. In addition, the correlation between boiling heat transfer and geometric characteristics of microchannel flow is also presented, and the future research direction of microchannel geometry design is discussed.

This study concerns a hybrid CPV (Concentrator Photovoltaic) system coupled with an Organic Rankine Cycle (ORC), which mainly contains CPV modules and cooling subsystem. The cooling fluid driven by pump is evaporated in tubes under the CPV modules. The superheated vapor of working fluid is generated for additional electric power generation with an ORC. Through the study of the impact of different parameters on the system, the efficiency of CPV-ORC combined system is compared with that of single CPV system. When the temperature of CPV cells increases, the combined system can effectively cooling the CPV and increase the additional energy generation.

Microchannel heat sink is one of the most promising cooling solutions for electronics with high heat flux. In order to further enhance the heat transfer performance of microchannel heat sink, a novel microchannel with rectangular grooves on the wall is designed, and the heat transfer and flow characteristics of Al2O3/water nanofluid in microchannels are numerically studied. The mixture model is used involving the slip velocity between nanoparticles and base fluid. By comparing with the conventional smooth channel, it's found that grooves are helpful to destroy and redevelop the thermal boundary layer. The disturbance by grooves also leads to much higher pressure drop through the channel than smooth one. This work will be helpful for the design of highperformance microchannel heat sink.