Investigation of geothermally sourced combined power and freshwater generation systems

To address the concurrent water and energy shortage issues regions where geothermal sources are abundant, three geothermally sourced combined power and freshwater generation technologies are investigated. Two of them are based on traditional power generation systems, including a steam system (SS) and a single flash system (SFS). The other one is a proposed trilateral flash system (TFS). Instead of focusing solely on their power generation potentials as previous geothermal exploitations did, the condensation process which produces desalinized freshwater is particularly investigated. To obtain a comprehensive evaluation, system performance under various geothermal wellhead conditions have been considered and compared. Results indicate that, for a typical liquid-dominated well, SS has absolute power generating advantage over SFS and TFS under low wellhead pressure and high wellhead vapor quality conditions. However, the TFS shows more stable power-generating and freshwater-generating performance when the wellhead condition varies, especially when the vapor quality gets lower. Efficiency of the total-flow turbine of TFS determines its system power potential. A turbine efficiency of 50% enables TFS to obtain comparable specific power with traditional power systems. Moreover, fresh water generation is a distinct advantage of the TFS, qualifying it a promising choice in remote arid geothermal terrains for both power and freshwater generation

Combined power and freshwater generation driven by liquid-dominated geothermal sources

In order to meet the twin challenges of energy shortage and water scarcity in eastern Africa, this paper looks at the feasibilities of using a geothermal water source to produce both fresh water and electricity. In this research, three geothermally sourced combined power and freshwater generation systems are investigated and compared. Two of them are based on traditional power generation systems, including a steam system (SS) and a single-flash system (SFS). The third one is a trilateral flash system (TFS) with a two-phase turbine, which processes the total geofluid flow from the wellhead directly. The power generation potential as well as the condensation process, which produces desalinized freshwater, are investigated for three systems under two typical liquid-dominated well conditions in the Aluto Langano geothermal field in Ethiopia. Results indicate that, suitable total flow turbine efficiency enables the trilateral flash system to be comparable with the steam system and the single-flash system regarding the power generation, especially when the well flow is more liquid dominated. Moreover, freshwater generation is a distinct advantage of the trilateral flash system, and its freshwater output can reach up to be 2.7 times higher than those of traditional systems, making it a promising solution for combined power and freshwater generation

Research on a coupled total-flow and single-flash (TF-SF) system for power and freshwater generation from geothermal source submitting

In response to the twin development challenges of energy shortage and water-scarcity in worldwide arid to semi-arid regions with geothermal resources, a new combined power and freshwater generation system is proposed for geothermal energy utilization. In this system, a total-flow turbine (TF) is employed to be coupled with the traditional single-flash (SF) system and thereafter the coupled TF-SF system is investigated in this work. In addition to power generation, the exhaust steam from turbines are recovered to produce freshwater through condensation. Based on the novel designed system, the production of both power and water are studied under variable wellhead conditions, including variable wellhead pressures, temperatures, mass flowrates, and vapor qualities. The temperature of the separating point at which the total-flow expansion ends and the steam expansion starts is studied for optimal system output. In addition, the efficiency effects of the total-flow turbine on performance of the combined system is also investigated. The power generation comparison shows good power potential of the proposed TF-SF combined system. An effective total-flow turbine with an average efficiency of 65% can lead to an optimal power capacity, exceeding the traditional single-flash (SF) system by 23.7%. Moreover, more than 1/3 of total wellhead discharge can be recovered as desalinated freshwater by the naturally equipped condensation process of the power plant, showing extra benefit from geothermal energy utilization

Which User-generated Content Should Be Appreciated More? - A Study on UGC Features, Consumers\u27 Behavioral Intentions and Social Media Engagement

Despite researchers have made a great deal of effort on exploring the reasons of travel consumers’ participation in UGC sites and the roles of these sites in different phases of their travel, knowledge on what factors influence travel consumers’ behavioral intentions in social media still remains largely unknown to both scholars and practitioners. With the attempts to find out this, we conducted a two-phase study on Chinese consumers. Utilizing the two sets of data we collected (npost = 65; nratings = 1668), we develop a multiple linear regression model to assess the influential factors in UGC sites on consumers’ behavioral intentions. Our results indicate that travel consumers’ purchase intention, word-of-mouth (WOM) intention, and attitudes towards destination brands are positively affected by the UGC features (creditability and interestingness) and consumers’ social media engagement (comment, retweet, and like).Further, inconsistent with the previous finding that credibility is a major concern in consumers’ information search processes, the interestingness of UGC is found to be more important

A Referral Rewards Incentive Dedign On Travel Consumer- Generated Content

User-generated content has become increasingly important to both tourism practitioners and travel consumers. Although prior studies have demonstrated how impactful UGC is and why marketing mavens employ UGC sites in their marketing campaigns, there is still scant evidence on how to successfully manipulate them. To fill this void, we conducted a two-phase experiment study. In the experiment, first, 65 tourists were invited then grouped according to three different treatments (namely, creating travel posts to achieve the maximum ‘comments’, ‘retweets’, or ‘likes’), and one will be rewarded if he/she achieves the goal. Second, for the manipulation check, we invited another group of Chinese consumers (n =268) to rate these travel posts based on their perceptions. Our experiment results indicate that this referral rewards incentive design has significant effects on consumers’ UGC perception (the credibility, interestingness, influence of postings), behavioral intentions (purchase intention, and WOM intention), and their likelihood of social media engagement (offering ‘likes’). In addition, we also discuss the implications of the results and how to exploit this design

How Referral Rewards Systems Shape What Tourists Share on Social Media

Sharing on social media not only relies on our intrinsic motivations but also can be induced by the extrinsic motivations such as referral rewards. Although our previous study demonstrated that incentivizing tourists to create postings could influence peer consumers’ behavioral intentions (i.e., purchase and word-of-mouth intentions) and social media engagement, we noticed that it was the content which was created under the incentive design drove all the impacts. Therefore, in this study, we extracted the content characteristics from the tourists’ postings we collected. Results indicated that the referral rewards systems (RRSs) we introduced could shape what tourists share, and the content characteristics such as positive emotional, utilitarian, high-level and low-level construal have different effects on peer consumers’ social media engagement and behavioral intentions. Our findings aid researchers and practitioners in understanding how to design successful RRSs and how to create viral content on social media

Exploring the Influence of User-Generated Content Factors on the Behavioral Intentions of Travel Consumers

Social media have been deemed as more and more critical to modern travel consumers. These consumers often regard social media as trustworthy source that can lower the perceived risk and uncertainty throughout their travel. Though previous studies revealed that travel consumers’ participation in social media could be explained by their functional, social-psychological and hedonic needs, the factors that impact their behavioral intentions, such as purchase intention, WOM intention, and attitudes of destination brands have not been well studied. By conducting a two-phase study on Chinese travel consumers (nposts =65; nratings=1668), we found that both the UGC features (credibility and interestingness) and the social media engagement of travel consumers (comment, retweet, like) can impact their behavioral intentions. In addition, compared to the credibility of a post, the interestingness could more positively influence the social media engagement of travel consumers. Our study gives a better understanding of connections between social media and the travel consumers’ behavioral intentions

Bioinspired heat exchangers based on triply periodic minimal surfaces for supercritical CO2 cycles

The supercritical carbon dioxide (sCO2) based Brayton cycle is a proposed alternative to replace conventional Rankine cycles in terms of high cycle efficiency, compact turbomachinery and heat exchangers. In the sCO2 cycle, however, the existing heat exchangers have been challenged by large portion of heat transfer (approximately 60–70% of total cycle heat transfer) and high cycle efficiency required. In the present study, two novel heat exchangers were proposed by utilizing triply periodic minimal surface (TPMS) structures. i.e. the Gyroid structure and Schwarz-D surface, to enhance heat transfer and improve cycle efficiency. TPMS structures are a class of structures composed of two distinct inter-penetrating volume domains separated by an area-minimizing wall, which have been observed as biological membranes and co-polymer phases. Two heat exchangers along with a reference printed circuit heat exchanger (PCHE) were investigated numerically by computational fluid dynamics simulations when the hot and cold sCO2 fluids pass through them at various Reynolds numbers. Effects of geometrical shapes and Reynolds number on the hydraulic and thermal performances were identified. It was demonstrated that two heat exchangers with TPMS can improve overall thermal performance by 15–100%, and the Nusselt number is raised by 16–120% for a given pumping power in comparison with the PCHE. Hence, heat exchangers with TPMS have a very good potential to enhance sCO2 cycle efficiency

Convective heat transfer in a thermal chimney for freshwater production in geothermal total flow systems

The convective heat transfer of air in a laboratory-scale thermal chimney with rectangular cross-section of constant area and two row electrical heaters simulating two heat exchangers was studied experimentally and numerically at 60–200 ℃ nominal temperatures of the top row heaters, 100 ℃ of the low row heaters and 20 ℃ ambient temperature to verify our design concept on freshwater production in geothermal total flow systems. Computational fluid dynamics simulations of air convective heat transfer were performed in ANSYS 2019R CFX based on the three-dimensional, steady Reynolds-averaged Navier-Stokes equations, Boussinesq buoyancy model, k-w turbulence model, and energy equation. The thermal radiation between heater surfaces and chimney walls was considered. The overall thermal and heat transfer characteristics, temperature and flow fields in the chimney were obtained. Effects of boundary condition of heater surface and thermal radiation between two row heaters on heat transfer were discussed. The thermal characteristics of the chimney with two row heaters are better than that with single row heaters. The predicted thermal power and convective Nusselt number agree with the experimental data, and the convective Nusselt number of the low row heaters is enhanced by (11.6–29.8) % compared with the single row heaters. The optimal operating nominal temperature of top row heaters should be higher than 140 ℃, and the optimal centre-to-centre row gap ratio is 5. Multiple jets in the gaps among the heaters and temperature jump crossing each row were observed. The maximum velocity and temperature jump rise with increasing heater nominal temperature

Particle Image Velocimetry (PIV) experimental study on the buoyant flow fields within a thermal chimney system for geothermal power plant

To enhance the air-cooling process in geothermal power plants for economical utilization of the exhaust steam from expansion, a natural-draft thermal chimney design was proposed and studied here in this paper. In view of the necessity of accurate velocity field measurements which would provide further insight into the physics behind the evolving plumes above heated horizontal cylinders, Particle Image Velocimetry (PIV) was employed to experimentally investigate the buoyant flow in the thermal chimney system. Two configurations have been tested to understand the flow induced by the horizontally heated cylinders inside the thermal chimney. Firstly, flow field above a single row of cylinders was tested while they were isothermally heated to simulate of an air-cooled condenser. After that, a second row of cylindrical heaters (air-heater) was added above the first row to enhance the buoyant flow, aiming at enhancing the air side flow of the air-cooled condenser. Flow characteristics and velocity enhancement were studied for both configurations. The results show that significant flow unsteadiness occur near the cylindrical heaters because of the non-steady crossing flows between adjacent cylinders, and the unsteadiness attenuates in the downstream. The effects of cylinder row distance, surface temperature as well as downstream distance on the flow field were then analyzed. Flow velocity is increased by the air-heater as the buoyancy force is enhanced, proving the idea of flow enhancement of the thermal chimney configuration. It is also observed that the velocity fluctuation, turbulent kinetic energy and vorticity change significantly after adding the second row of heaters. The present study provides further insight into natural convection flow theory of heated cylinders for a Rayleigh number range of 1.3E4 to 2.2E4, which is fundamental for the flow enhancement designing of the proposed natural-convection-driven cooling system