Recent Advances in Heat Pipes

Heat pipes are considered as an effective thermal solution, particularly in high heat flux applications and in situations where there is a combination of nonuniform heat loading, limited airflow over the heat-generating components, and space or weight constraints. This book is intended to explore some of the recent advances in heat pipes and their applications in thermal systems. The first chapter is an introductory chapter about the recent advances in heat pipes in general. The second chapter is about thermosyphon heat pipe technology; working principles, advantages, and disadvantages; application ranges; and using computational fluid dynamics in modeling thermosyphons. The third chapter is about recent research into loop heat pipes (LHPs). The last chapter presents a novel liquid-vapor separator-incorporated gravitational LHP

A Preliminary Study of Internal Corrosion in Condensate Pipelines at Geothermal Power Plants

In this study, we presented observations and analyze related to internal corrosion in condensate pipes in geothermal power plants. A damaged pipe of condensate pipeline taken from a power plant was investigated to determine the root cause of failure. The observation and failure analysis was carried out by visual and dimensional examination, chemical composition testing, macroscopic, and microscopic examination, Scanning Electron Microscope (SEM) examination with Energy Dispersed Spectrometer (EDS). The deposit in the pipe was analyzed by X-Ray Diffraction (XRD). The quality of the condensate fluid and their tendencies were determined by Langelier Saturation Index (LSI). Also, the corrosion rate of the pipe was simulated by condensate fluid by using a corrosion measurement system (Tafel polarization). The internal corrosion was found in the condensate line is strongly suspected to occur due to erosion-corrosion. Erosion corrosion is caused by insoluble and hard particles in the condensate fluid. The results of XRD found the presence of calcium-silicate compounds in the sediment that is suspected to be the cause of erosion particles. The reduction of the thickness of the bottom pipe wall and occurs in longitudinal directions the alleged damage to the pipe due to sediment corrosion. The presence of hard compounds and differential oxygen can accelerate the process of corrosion so that the corrosion rate in condensate pipelines was a category in the severe category based on NACE SP0775 standards

Investigation of a super performance dew point air cooler and its application in buildings

Based on extensive literature reviews, technical opportunities were identified to improve the energy efficiency of a dew point air cooler. This applied research aimed to develop a super-performance dew point air cooler to replace or partly replace the conventional energy-intensive air conditioners applicable to buildings.This research followed the methodology of combined theoretical and experimental investigation and a procedure of concept formation, validating and updating. A simulation software was developed and validated to investigate the impacts of the geometric configuration and operational conditions on the unit’s cooling performance and assist the prototype design. As a result, a novel dew point air cooler prototype, featuring innovative structure of the heat and mass exchanger, application of new materials and new processes, unique water distribution and control scheme and exclusive self-developed simulation software, was constructed and tested under controlled laboratory environment. Two patents were generated, one of which has been authorized by the China State Intellectual Property Office and the other has been filed in the Intellectual Property Office of the United Kingdom.Under standard testing conditions, i.e. dry-bulb temperature of 37.8oC and the coincident wet-bulb temperature of 21.1oC, the prototype cooler achieved a wet-bulb cooling effectiveness of 114% and dew-point cooling effectiveness of 75%, yielding a significantly high Coefficient of Performance (COP) of 52.5 at the optimal working air ratio of 0.364. The performance testing was also carried out under various simulated conditions representing the climates of hot & dry, warm & dry, moderate, warm & humid and the wet-bulb effectiveness of the prototype kept in the range 112% to 128% and dew-point effectiveness of 67%-76%, giving a COP of 37.4-52.5. Compared to the conventional vapour compression air conditioners which have a COP of around 3, the prototype cooler had 11-17 times higher COP, leading to a reduction in electrical power consumption by around 92% to 94%.A dedicated case study of the proposed dew point cooler based on conditions in Beijing, a representative city in warm and humid climate, was carried out to predict the annual operational performance, economic rewards, and associated environmental benefits. Compared to the conventional packaged air conditioners, 91.4% of annual power demand could be saved. The annual water consumption is less than 0.3 tonnes to provide the cooling of 2428.1 kWh. And the payback period of static investments would be less than 4 years to replace an equivalent packaged air conditioner.A significant leap forward has been achieved with this study and this is expected to open enormous global business in the very near future, thus bringing about great economic, environmental and sustainability benefits worldwide

FOULING AND ITS MITIGATION ON HEAT EXCHANGER SURFACES BY ADDITIVES AND CATALYTIC MATERIALS

Calcium carbonate (CaCO3) fouling is the most commonly observed fouling phenomenon in cooling water applications. Fouling happens when a process uses cooling water supersaturated with mineral salt crystals (i.e. hard water). Precipitation deposits on heat transfer surfaces whenever these inversely-soluble salt crystals, like dissolved calcium ions, are exposed to high temperature. An online-monitoring system for fouling phenomena was studied experimentally using a mixture of sodium bicarbonate and calcium chloride for carbonate fouling salt in de-ionized water. The effects of different parameters such as surface temperature, flow velocity, and concentration on the calcium carbonate scale formation process were experimentally investigated by using the developed monitoring system. The calcium carbonate deposition rates on five different metal surfaces (Stainless steel 316, brass, copper, aluminum and carbon steel) were investigated. The surface was analyzed by analytical microscopy to investigate the morphology of the deposit layer. The results revealed that SS316 yielded the lowest deposition on the surface. Nowadays, hazardous chemical additives are often used to mitigate fouling but chemicals are expensive and pose problems to the environment. Physical water treatment (PWT), a non-chemical method is good alternative for fouling mitigation method. PWT using zinc and tourmaline as catalytic materials is presented in this research work. Fouling tests were conducted for verification of this PWT method. Artificially-hardened water at 300 mgL-1 was utilized as the fluid medium to form fouling deposits. The hard water flow velocities were varied from 0.15 ms-1 to 0.45 ms-1 and the artificially-hardened water temperature was maintained at 25 oC and the experimental time was set to 72 hours for each run. The results revealed that in the PWT-treatment case, the deposition of calcium carbonate particle is lower compared to those in the No-treatment case. Furthermore, mitigation of calcium carbonate fouling by applying EDTA, EDTA-MWCNT and DTPA-MWCNT-based water nanofluids on heat exchanger surfaces were reported. Investigation of additive (benign to the environment) on the fouling rate of deposition was performed. Assessment of the deposition of calcium carbonate on the heat exchanger surfaces with respect to the inhibition of crystal growth was conducted by Scanning Electron Microscope (SEM). The results showed that the formation of calcium carbonate crystals can be retarded significantly by adding MWCNT-DTPA additives as inhibition in the solution. Moreover, investigation was extended by introducing a non-invasive-monitoring of concentrations of calcium hardness in cooling water. Investigation was conducted with a 2.5 GHz microwave cavity resonator. The principle of electric dipole moment theories were used to analyse the sample solution that occurs as a function of calcium ion content. The sample was centrally positioned in the electric field of the TM010 mode of a resonant cylindrical cavity. COMSOL simulation package was used to compare and validate the experimental cavity resonator frequency. Transmission signal (S21) measurements via Vector Network Analyser (VNA) with different concentrations were investigated and observed linear relationship in amplitude with frequency changes. These research successfully introduce a novel technique of monitoring of water hardness concentration by using non-invasive microwave sensor

The use of metal hydrides in fuel cell applications

This paper reviews state-of-the-art developments in hydrogen energy systems which integrate fuel cells with metal hydride-based hydrogen storage. The 187 reference papers included in this review provide an overview of all major publications in the field, as well as recent work by several of the authors of the review. The review contains four parts. The first part gives an overview of the existing types of fuel cells and outlines the potential of using metal hydride stores as a source of hydrogen fuel. The second part of the review considers the suitability and optimisation of different metal hydrides based on their energy efficient thermal integration with fuel cells. The performances of metal hydrides are considered from the viewpoint of the reversible heat driven interaction of the metal hydrides with gaseous H2. Efficiencies of hydrogen and heat exchange in hydrogen stores to control H2 charge/discharge flow rates are the focus of the third section of the review and are considered together with metal hydride-fuel cell system integration issues and the corresponding engineering solutions. Finally, the last section of the review describes specific hydrogen-fuelled systems presented in the available reference data.IS

Optimization of a District Heating energy supply system under a cost-effectiveness perspective

xi, 62 p.The necessity to reduce greenhouse gas (GHG) emissions is a world global challenge that is reflected in numerous international, agreements, national and local regulations. Build-ings stand out as one of the sectors that require a significant amount of energy, hence building efficiency optimization and incorporation of renewable energy sources (RES) is a constant tendency aimed at leading to the creation of concepts, such as nearly Zero Emission Buildings (nZEB). In this respect, the potential for reducing energy consumption in the building stock evolving towards districts scale, which can play a significant role in the energy transition of the stock, as its tackle larger scale of projects. To this end, along with passive energy efficiency measures (EEM) district heating (DH) is one of the options for the reduction of energy consumption and emissions from heat production. The thesis concerns optimization of the district heating network under the cost-effec-tivity analysis of centralized energy supply systems (ESS) in conjunction with passive EEM, and RES for the Otxarkoaga neighbourhood in Bilbao. For this purpose, based on a simplified model (131 buildings) of the neighbourhood created in the Design Builder program the set of ESS scenarios for the DH network has been designed, described, and simulated. Following that, simulation output has been analysed by energy demand and ESS consumption within a set of applied EEM at the district level. In total 60 combina-tions have been considered. Also, the DH network topology was proposed, and distribu-tion heat losses were characterized. Finally, the economic study of considered ESS tech-nologies of DH network analyzed under the cost-effectiveness perspective and compara-tive characteristics of the district to individual building renovation is carried out. The study showed that centralised heating could be cost-effective for a considered neighbourhood within some technologies. The biomass boiler ESS can have renovation combination with the lowest investment in 10,000 € per building, and geothermal solution, being highly investment, can reach the lowest energy consumption

Overview on the hydrodynamic conditions found in industrial systems and its impact in (bio)fouling formation

Supplementary data to this article can be found online at https://doi.org/10.1016/j.cej.2021.129348.Biofouling is the unwanted accumulation of deposits on surfaces, composed by organic and inorganic particles and (micro)organisms. Its occurrence in industrial equipment is responsible for several drawbacks related to operation and maintenance costs, reduction of process safety and product quality, and putative outbreaks of pathogens. The understanding on the role of operating conditions in biofouling development highlights the hydrodynamic conditions as key parameter. In general, (bio)fouling occurs in a higher extension when laminar flow conditions are used. However, the characteristics and resilience of biofouling are highly dependent on the hydrodynamic conditions under which it is developed, with turbulent conditions being associated to recalcitrant biodeposits. In industrial settings like heat exchangers, fluid distribution networks and stirred tanks, hydrodynamics play a dual function, affecting the process effectiveness while favouring biofouling formation. This review summarizes the hydrodynamics played in conventional industrial settings and provides an overview on the relevance of hydrodynamic conditions in biofouling development as well as in the effectiveness of industrial processes.This work was financially supported by: Base Funding - UIDB/00511/2020 of LEPABE and UIDB/00081/2020 of CIQUP funded by national funds through the FCT/MCTES (PIDDAC); Project Bio cide_for_Biofilm - PTDC/BII-BTI/30219/2017 - POCI-01-0145-FEDER 030219, ABFISH – PTDC/ASP-PES/28397/2017 - POCI-01-0145- FEDER-028397 and ALGAVALOR - POCI-01-0247-FEDER-035234, fun ded by FEDER funds through COMPETE2020 – Programa Operacional Competitividade e Internacionalizaçao ˜ (POCI) and by national funds (PIDDAC) through FCT/MCTES; Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit and BioTecNorte operation (NORTE-01-0145-FEDER 000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte; FCT/ SFRH/BD/147276/2019 (Susana Fernandes) and SFRH/BSAB/150379/2019 (Manuel Simoes).info:eu-repo/semantics/publishedVersio