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Abstract Matrix-embedded, surface-attached microbial communities, known as biofilms, profusely colonise industrial cooling water systems, where the availability of nutrients and organic matter favours rapid microbial proliferation and their adhesion to surfaces in the evaporative fill material, heat exchangers, water reservoir and cooling water sections and pipelines. The extensive growth of biofilms can promote micro-biofouling and microbially induced corrosion (MIC) as well as pose health problems associated with the presence of pathogens like Legionella pneumophila. This review examines critically biofilm occurrence in cooling water systems and the main factors potentially affecting biofilm growth, biodiversity and structure. A broad evaluation of the most relevant biofilm monitoring and control strategies currently used or potentially useful in cooling water systems is also provided. This review critically examines the main factors affecting biofilm growth in cooling water systems together with the monitoring and control strategies currently used or potentially useful in full scale plants.

During the operation of the circulating cooling water system, inorganic scale deposition may cause technical problems, such as reduction of heat transfer efficiency in cooling systems and obstruction of pipes. In the industry, chemicals are often used as scale inhibitors in scale deposition control, antiscalants popular in industry are generally phosphorus and nitrogen-containing chemicals, which may lead to eutrophication. However, increasing environmental concern and discharge limitations have guided antiscalants to move toward biodegradability, nontoxicity and cost–effectiveness. This paper reviews current research on the application of using bio-materials as scale inhibitors, including proteins and amino acids, polysaccharides, plant extracts, microbial reagents, and microbiological products. The non-bioaccumulation, low cost, readily biodegradability and sustainably available characters promote the development of green-scale inhibitor chemistry.

According to future predictions, reliance will be largely on solar panels to provide electrical energy. Given its importance, the factors that maintain or increase its efficiency must be studied. Among the factors that reduce its efficiency are temperature, shade, dust and many others. The effect of the temperature on the performance and efficiency of a photovoltaic (pv) panel is the one of the main important facing the renewable energy, especially in hot regions, e g. South part of iraq. The high temperature to which the pv module is exposed in hot weather reduces the open circuit voltage and the efficiency. In this work, use two methods for cooling, namely water cooling and air cooling. The first method of cooling was air cooling by using dc fan that placed in the back of pv module. While the second method water cooling divided in two techniques, the first technique done by using two pieces of aluminum for cooling (water cooling blocks) placed in the rear of pv module and the second technique of water cooling by using copper perforated tube for spraying water placed in the front of pv module. The average of experimental results shows that the use of technique spraying water cooling are highest enhancement in efficiency than others techniques (water cooling blocks and dc fan) and more effective at high pv temperatures.

Deep Q Network (DQN) is an efficient model-free optimization method, and has the potential to be used in building cooling water systems. However, due to the high dimension of actions, this method requires a complex neural network. Therefore, both the required number of training samples and the length of convergence period are barriers for real application. Furthermore, penalty function based exploration may lead to unsafe actions, causing the application of this optimization method even more difficult. To solve these problems, an approach to limit the action space within a safe area is proposed in this paper. First of all, the action space for cooling towers and pumps are separated into two sub-regions. Secondly, for each type of equipment, the action space is further divided into safe and unsafe regions. As a result, the convergence speed is significantly improved. Compared with the traditional DQN method in a simulation environment validated by real data, the proposed method is able to save the convergence time by 1 episode (one cooling season). The results in this paper suggest that, the proposed DQN method can achieve a much quicker learning speed without any undesired consequences, and therefore is more suitable to be used in projects without pre-learning stage.

The thermal error suppression rate depends on the cooling effect of the water cooling system, and the cooling water flow rate is a direct factor affecting the cooling effect. To better reduce the thermal error, a numerical model of cooling water is established to solve for the optimal cooling water flow rate. Firstly, a numerical model of thermal deformation of the pendulum angle milling head is established based on thermoelasticity theory to determine the main heat sources leading to thermal deformation. Then, a numerical analysis model of the cooling water flow rate is established to investigate the cooling water flow rate that has the best effect on the suppression of thermal errors. Finally, five flow rates are used for cooling experiments to verify the accuracy of the numerical model. The results show that the temperature of each measurement point increases with the flow rate from a significant decrease to the basic constant trend of gradual saturation. The reduction rate of thermal error at v =54 cm/s is as high as 73.4%, providing a theoretical basis for enterprises to optimize water cooling system parameters.

In the process of geothermal energy exploitation, granites undergo cyclic heating and water cooling due to the heat conduction from distant rock mass to the cooled rock. The mechanical response, deformation and acoustic emission (AE) characteristics of granite treated by cyclic heating (150–300 °C) and water cooling (1–15) under the coupling action of compressive and shear stress were analyzed by preset angle shear tests in three preset angles (45°, 55°, 65°) at macroscopic level. Given that the peak strength of granite shows an accelerating downward trend with the increase of heating temperature and cycle times. The cohesion of granite declines, and the internal friction angle increases in general. AE activities are active throughout the loading process, which shows ductile failure characteristics of granite obviously. The accumulative AE events decrease by 69.3% with increasing heating temperature (150–600 °C), and 82.4% with increasing cycle times (1–15). The crack initiation area gradually shifts from the two ends of sample to the middle area with the increasing thermal damage. Shear behaviors inside the granite start earlier and last for a longer period, which results in the complex fracture network distribution of turtle shape and the shearing failure of “Z” shape on the surface of 600-1 sample. Scanning electron microscopy (SEM) was conducted to reveal the microscopic mechanism of thermal damage. Given that the intergranular and transgranular cracks induced by the uneven expansion of particles connect with each other and form a complex crack network as the thermal damage increasing. The continuous heating with high temperature causes minerals to melt and deform, resulting in the decrease of bonding strength between particles. All above results can provide references for the analysis and prediction of rock stability of granite in Enhanced Geothermal Systems (EGS) project.

The main problem in the operation of nuclear power plants (NPPs) is the scale formation of mineral impurities in an open recirculating system (ORS). The discharge of water from an ORS into natural water bodies can alter the chemical equilibrium of wastewater components, necessitating continuous monitoring. The purpose of this study was to analyse the behaviour of dissolved inorganic salts (DIS) in water within an ORS during water treatment, using the Rivne Nuclear Power Plant (RNPP) as a case study. Moreover, the analysis impact of their discharge with return water in the Styr River. The DIS concentration has a significant impact on the efficiency of the system and the environmental of an ORS power plant. Altogether, each of the DIS components was analysed separately using the standard measurement methods, statistical methods of data processing and correlation analysis. In addition, the annual discharge of the DIS components was calculated, and the amount of discharge was assessed for compliance with the maximum discharge limit. Thus, the impact of the formation of DIS and the variations in their concentration levels upon the discharge of wastewater into a natural water body were examined.

A biological method was developed for reusing urban reclaimed water in circulating cooling water systems (CCWS), in which the compound microorganism preparation (CMP) mainly included nitrobacteria, Bacillus subtilis, photosynthetic bacteria and Thiobacillus denitrificans, was used to control the scaling, corrosion and biofouling of CCWS. The abundant carbon, nitrogen and phosphorus in urban reclaimed water met the needs of microbial growth. Compared with chemical agents, CMP had the advantages of high efficiency, no additional chemicals and being more economical. The research results showed that CMP improved water quality and decreased ammonia nitrogen (NH3-N) and chemical oxygen demand (COD). The concentration ratio of CCWS reached 3.87 using CMP. The corrosion inhibition rate of CMP and the removal rate on biofouling achieved 99.69% and 22.21%, respectively. The mechanisms of CMP to control scaling, corrosion and biofouling were discussed, and the surface characteristics and chemical compositions of corrosion products and biofouling were analyzed.

Laboratory tests were conducted to study the physical and mechanical properties of granite after heating and water-cooling treatment for 1 and 30 cycles from room temperature to 500 °C. The change mechanisms for the water-cooling treatment were analysed via scanning electron microscope observation. At 500 °C, the volume of granite increases by 1.73% and 2.55%, the mass decreases by 0.16% and 0.31%, and the density decreases by 1.86% and 2.78% after 1 and 30 thermal cycles, respectively. The average values of UCS and E after 1 and 30 cycles both decrease as the temperature rises, while the peak strain exhibits the reverse trend. A yield platform is observed in the yield stage of the stress–strain curve above 300 °C, and the ductility of granite gradually increases with temperature. The normalized P-wave is linear with respect to the normalized UCS and E at 1 thermal cycle, whereas it shows exponential relationships with the normalized UCS and E at 30 thermal cycles. The degradation of the physical and mechanical properties of granite after 1 and 30 cycles is mainly caused by the generation and development of microcracks inside the rock. Compared to 1 thermal cycle, more microcracks are observed at 30 thermal cycles. Therefore, the thermal cyclic treatment can further deteriorate and weaken the physical and mechanical properties of granite.

Although point load strength is considered as a best proxy for uniaxial compressive strength and also incorporated in the routinely used rock mass rating (RMR) system, the effects of temperature treatments on the point load strength has not gained ample attention over the years. Accordingly, in this investigation, two different cooling techniques (i.e. water- and air-cooling methods) has been used in order to study the influence of different heating–cooling treatments on the physical properties, microstructural characteristics and point load strength of Himalayan granite collected from Sangla valley, Himachal Pradesh. The temperatures for heat treatment were targeted at 100 °C, 200 °C, 300 °C, 400 °C, 500 °C and 600 °C. As a response to thermal treatments, increase in effective porosity, decrease in density and increase in damage coefficient occurs which causes exponential decrease in point load strength. It decreases as high as 74% and 81% under air-cooling and water cooling, respectively, after heating of about 600 °C with reference to thermally untreated specimens. The microstructural study reveals that the grain boundary is quite intact, and the thermal-induced cracks are less pronounced up to 200 °C in both the thermal treatments. However, the increase in crack density due to thermal stresses and thermal shocks induce additional micro-cracks like intra-, inter- and trans-granular cracks, at and beyond 300 °C onwards and their coalescence with each other at higher temperatures (i.e. ≥ 500 °C) under both the thermal treatments contribute towards the variation in point load strength of thermally treated granites.