Decrease In Ambient Temperature Research Articles

Experimental Investigation on Thermal Runaway of Lithium-Ion Batteries under Low Pressure and Low Temperature

Understanding the thermal runaway mechanism of lithium-ion batteries under low pressure and low temperature is paramount for their application and transportation in the aviation industry. This work investigated the coupling effects of ambient pressure (100 kPa, 70 kPa, 40 kPa) and ambient temperature (−15 °C, 0 °C, 25 °C) on thermal behaviors in an altitude temperature chamber. The experimental results indicate that lowering ambient pressure and temperature could attenuate the thermal runaway intensity, which is mainly attributable to the reduction in oxygen concentration and the increase in heat loss. Such a dual effect leads to the maximum temperature decreasing from 811.9 °C to 667.5 °C, and the maximum temperature rate declines up to 2.6 times. Correspondingly, the whole thermal runaway process is deferred, the total time increases from 370 s to 503 s, and the time interval, Δt, from safety venting gains by 32.3% as the ambient pressure and temperature decrease. This work delivers an in-depth understanding of the thermal characteristics under low pressure and low temperature and provides meritorious guidance for the safety of cell transportation in aviation.

Experimental Investigation on Thermal Runaway of Lithium-Ion Batteries under Low Pressure and Low Temperature

Understanding the thermal runaway mechanism of lithium-ion batteries under low pressure and low temperature is paramount for their application and transportation in the aviation industry. This work investigated the coupling effects of ambient pressure (100 kPa, 70 kPa, 40 kPa) and ambient temperature (−15 °C, 0 °C, 25 °C) on thermal behaviors in an altitude temperature chamber. The experimental results indicate that lowering ambient pressure and temperature could attenuate the thermal runaway intensity, which is mainly attributable to the reduction in oxygen concentration and the increase in heat loss. Such a dual effect leads to the maximum temperature decreasing from 811.9 °C to 667.5 °C, and the maximum temperature rate declines up to 2.6 times. Correspondingly, the whole thermal runaway process is deferred, the total time increases from 370 s to 503 s, and the time interval, Δt, from safety venting gains by 32.3% as the ambient pressure and temperature decrease. This work delivers an in-depth understanding of the thermal characteristics under low pressure and low temperature and provides meritorious guidance for the safety of cell transportation in aviation.

Evaluation of Thermal Insulation of Vacuum-Insulated Casing to Prevent Uncontrollable Melting of Ice and Borehole Instability in Permafrost

During oil and gas development in permafrost, hot fluids within the wellbore can cause ice melting around wellbore and a decrease in sediment strength, as well as wellbore instability. In the present work, the experimental system for evaluating the insulation effectiveness was established, and the applicability of this experimental system and methodology was verified. It was found that the difference between the experimentally obtained and actual thermal conductivity of the ordinary casings are all within 1.0 W/(m·°C). Meanwhile, the evaluation of insulation effect found that the decrease in fluid temperature, ambient temperature, and vacuum degree can improve its insulation performance. Finally, the numerical simulation was conducted on ice melting and borehole stability during the drilling operation in permafrost. The investigation results demonstrate that the use of vacuum-insulated casings significantly reduces the total heat transferred during the simulation by 86.72% compared to the ordinary casing. The utilization of vacuum-insulated casing reduces the range of ice melting around wellbore to only 16%, which occurs when using ordinary casing. The use of the vacuum-insulated casing resulted in a reduction in the final borehole enlargement rate from 52.1% to 4.2%, and wellbore instability was effectively suppressed.

ESTIMATION OF THE POSTMORTEM INTERVAL BY CRANIOENCEPHALIC THERMOMETRY WITH A SINGLE DISCRETE DECREASE IN AMBIENT TEMPERATURE

Aim– development of a method implemented in the format of a computer program for determining the postmortem interval (PMI) by cranioencephalic temperature (CT) of a corpse under conditions of cooling with a single discrete decrease in ambient temperature. Material and methods. Analytical and finite element modeling of CT dynamics with a single discrete decrease in ambient temperature is performed. Results. A mathematical model has been developed for determining the PMI and the uncertainty of its estimates with a single discrete decrease in the ambient temperature. The values of the constants of the model equation and their variances are determined on the basis of finite element modeling of CT dynamics under the specified cooling conditions. The computational algorithm of the specified method for determining PMI and contraindications to its use are implemented in the C# language in the form of the Warm Bodies DSC program. Conclusion. The developed method and the application implementing it are recommended for use in forensic medical practice to determine the PMI with a single discrete decrease in ambient temperature.

Study on the influencing factors of impact resistance of shear thickening fluids filled foam

PurposeThe present study assesses the impact resistance of the shear thickening fluids-filled (STFs-filled) foam through drop-hammer impact tests.Design/methodology/approachThe maximum residual impact load and specific impact energy absorption rate of STF-filled foam are studied with varying thickness (4–14 mm), densities (0.35–0.6 g/cm3) and hardness (40–50 Rockwell Hardness C Scale (HRC)) under different ambient temperatures (−20−20 °C) and impact energies (25–75 J).FindingsThe following conclusions are obtained from this study: (1) the higher the impact energy, the greater the maximum residual impact force and energy absorption efficiency of the material; (2) the impact resistance of STF-filled foam can be improved with the decrease of ambient temperature, achieving the highest energy absorption rate at −10?. (3) STF-filled foam substrate has the highest impact resistance, the lowest maximum residual impact force and the highest energy absorption coefficient when the density is 0.35 g/cm3, the hardness is 45HC and the thickness is 10 mm.Originality/valueThis is the first paper to analyze the impact of both environmental factors and material properties on the impact resistance of STF-filled foam. The results show that the decrease in temperature and the increase in hardness can enhance the impact resistance of STF-filled foam.

Experimental study and exergy analysis of electric vehicle single-stage compression secondary throttling CO2 air-source heat pump system in cold climate

A novel CO2 air-source heat pump system (ASHPs) with a secondary throttling based on a single-stage compression was proposed to further improve the heating energy efficiency of electric vehicles (EVs) for heating in cold climates. The heating characteristics of the secondary throttling system (STS) and conventional throttling system (CTS) at different indoor air supply temperatures were compared. The STS performance characteristics were investigated under varying ambient temperature, outdoor air velocity, and exergy analysis was performed on the system and its components. A fitting correlation equation for optimal discharge pressure was obtained based on experimental data. The results demonstrate that implementing STS significantly reduces CO2 ASHPs energy consumption (Wcom), enhances the coefficient of performance (COP), and reduces exergy destruction. When the indoor air supply temperature reaches 45 °C, using STS can result in an 8.1 % reduction in Wcom, a 9.4 % increase in COP, and a 6.1 % improvement in the exergy efficiency (Exη) compared to that of CTS. Furthermore, the advantages of STS become more pronounced with higher indoor target air supply temperatures. As the ambient temperature decreases, the exergy efficiency of the STS reaching the target air supply temperature decreases. The velocity of outdoor air significantly affects the STS performance, and increasing outdoor air velocity can effectively enhance the Exη of STS. The optimal discharge pressure fitting equation for the STS was obtained through multiple linear regression analysis. These findings can provide ideas for architectural optimization and design of CO2 ASHPs for EVs, which are important for further improving system performance.

Recovery of engine waste heat in low temperature environment of plug-in hybrid electric vehicle

The performance and life of electric vehicle power batteries will be reduced at low temperatures, and the lower temperature in the electric vehicle will also affect the comfort of drivers and passengers. Taking into account the winter temperatures and the unique drive structure of the plug-in hybrid electric vehicle, a specially designed driving mode for low-temperature environment is implemented. Based on this drive mode, a plug-in hybrid electric vehicle (PHEV) integrated thermal management structure is proposed to heat the battery and the passenger compartment, thereby improving energy efficiency. A mathematical model is used to establish the entire vehicle thermal management system, which is then experimentally validated. Under the NEDC (New European Driving Cycle) at ambient temperatures of −5°C, −10°C, −15°C, and −20°C, the calculation results of engine waste heat utilization and PTC (Positive Temperature Coefficient) heating are compared and analyzed. The results show that the average heating rate of the thermal management system proposed in this study is 23% faster than that of PTC heating at low temperature. The SOC decreases to 63.43% when engine waste heat utilization is adopted. When PTC heating is used, the SOC decreases to 49.18%. However, the advantage of the faster rate of engine waste heat compared to PTC heating becomes less pronounced as the ambient temperature decreases.

A numerical study of cucurbit cultivation in a greenhouse under direct solar radiation and equipped with a direct evaporative cooler in summer season

The performance of direct evaporative cooler to meet cooling demand of a greenhouse in Tehran in the hottest months of the year as well as water and electricity consumption were numerically studied. The suitable values of air change per hour (ACH) was also obtained for cultivation of tomato, cucumber, eggplant and bell peppers. The k-Ԑ Realizable Turbulence and Discrete Ordinates (DO) models was used for simulating the airflow and estimating radiative heat transfer, respectively. The results showed that an ACH of 10 is proper for tomato cultivation. When the ambient temperature is maximal, an ACH of 15 can be used for cucumber cultivation. However, ACH cannot be kept constant, and ACHs of ≤10 should be utilized when the ambient temperature decreases. For eggplants, it is better to use an ACH 20 at hot hours and an ACH of 10 when the temperature declines. For the bell pepper plant, 20 and 10 ACHs are suitable for day and night hours, respectively. Moreover, the maximum daily water consumed in the greenhouse happens in August and equals 222 lit/day for 20 Air Changes per Hour (ACH). The minimum daily water is consumed in July, equaling 106 lit/day for an ACH of 10. In the present study, the electricity rate consumed in the greenhouse equals 127W when ACH = 20, i.e., the consumed electric energy is 3 kWh for the entire system in a 24-h interval.

Ambient Temperature and Cardiac Biomarkers: A Meta-Analysis.

This study quantified the effect of cold or heat exposure of ambient temperature on the alteration of well-known cardiac markers. A meta-analysis was performed using the PRISMA guidelines. Peer-reviewed studies on ambient temperature and cardiac biomarkers were retrieved from MEDLINE, ScienceDirect and Google Scholar from January 2000 to February 2022. The pooled effect sizes of ambient temperature on cardiac biomarkers c-reactive protein, soluble-cell adhesion-molecule-1, soluble-intercellular-adhesion-molecule-1, total cholesterol, low-densitylipoprotein, interleukin-6, B-type-Natriuretic-Peptide; systolic/diastolic blood pressure were quantified using a random-effects meta-analysis. A total of 26 articles were included in the metaanalysis after screening the titles, abstracts and full texts. The pooled results for a 1°C decrease of ambient temperature showed an increase of 0.31% (95% CI= 0.26 to 0.38) in cardiac biomarkers (p=0.00; I-squared=99.2%; Cochran's Q=5636.8). In contrast, the pooled results for a 1°C increase in ambient temperature showed an increase of 2.03% (95% CI= 1.08 to 3.82) in cardiac biomarkers (p=0.00; I-squared=95.7%; Cochran's Q=235.2). In the cardiovascular (CV) population, the percent increase in cardiac biomarkers levels due to a decrease/increase in ambient temperature was greater. This study showed the decrease/increase in ambient temperature has a direct correlation with the alterations in cardiac biomarkers. These findings are useful for managing temperatureassociated cardiovascular mortality.

Performance of an automotive reversible CO2 heat pump system during periodic frosting-defrosting cycles

Electric vehicles (EVs) have seen rapid growth in the global market share due to the demand for low-emission commuting. However, EVs face the challenge of range anxiety in cold weather due to the capacity degradation of lithium-ion batteries and the increased demands of cabin and battery heating. Heat pump (HP) technology improves the heating efficiency compared to resistive heating, but in cold and humid weather, frost can grow on the outdoor evaporator and reduce the efficiency of the HP system. In this paper, experiments are carried out to assess the impacts of ambient temperature and relative humidity (RH) on the capacity and efficiency of a transcritical CO2 HP system during the continuous frosting-defrosting cycles under some challenging operating conditions (ambient temperature below 0 °C and RH over 80%). Moreover, the mass of frost accumulated during the frosting period, and that of water retained, drained, and vaporized during the defrosting period are measured and analyzed. The results show that when the ambient temperature decreases from 0 to −10 °C, the peak value of the heating capacity in the first frosting or HP mode period reduces from 4.85 to 3.54 kW, and the coefficient of performance (COPhp) drops from 1.61 to 1.47, but the operating time of the first frosting period significantly increases from 32 to 108 min. Similarly, lowering RH from 90% to 80% at 0 °C also helps to extend the operating time of the frosting period in one frosting-defrosting cycle from 32 to 84 min. In addition, with the current commonly used defrost initiation criterion, which is the air-side pressure drop across the outdoor evaporator increasing by five times, the heating capacity and system efficiency drop by less than 10% at the end of one frosting period. This indicates the potential for a longer operating time of the HP system which could reduce the undesirable impact on the passengers’ comfort during the reversed cycle defrosting.

Experimental analysis of the air-to-water ejector-based R290 heat pump system for domestic application

The aim of this study was to analyze and compare the performance of an 8 kW ejector-based R290 heat pump system for hot water heating applications that operates with two different expansion devices: a throttling valve and a two-phase ejector. The vapor compression system was designed to compare the unit operating in direct expansion and ejector-based working modes under similar operating conditions. The test results were assessed for overall system performance measured by COP and heating capacity and for single-component operation. The ejector mode allowed operation at the same range of ambient temperatures as direct expansion mode with the potential to completely replace the expansion valve. The COP of ejector system was up to 2.6, which was 38% higher than direct expansion when working under similar conditions for an ambient temperature of −12.8°C. Moreover, the COP in direct expansion mode decreased significantly along the decrease of ambient temperature, whereas for the ejector mode this decrease was considerably smaller.

Effect of Refrigerated Inlet Cooling on Greenhouse Gas Emissions for a 250 MW Class Gas Turbine Engine

In this study, the effect of inlet air cooling on greenhouse gas (GHG) emissions and engine performance for a land-based gas turbine engine was investigated under varying ambient temperatures (15–55 °C). The study aimed to reduce GHG emissions while improving output power and fuel efficiency during hot weather operating conditions. For illustrative purposes, a representative gas turbine engine model, approximating the 250 MW class General Electric (GE) engine, was analyzed in a simple cycle. A refrigeration process was integrated with a turboshaft gas turbine engine to chill the incoming air, and the power required for cooling was extracted from the gas turbine’s output power. This mechanical chiller was assumed to provide a 15 °C inlet air temperature. Without inlet air cooling, at 55 °C ambient temperature, the engine’s power output was calculated to decrease by 15.06%, while power-specific fuel consumption and GHG emissions increased by 6.09% and 5.84%, respectively. However, activating the refrigeration or cooling system in the inlet made it possible to mitigate most of the adverse effects of hot weather on the engine’s performance and GHG emissions. Therefore, with inlet air cooling, the power output loss reduces to 3.28%, indicating an 11.78% recovery compared to the 15.06% loss without cooling. Similarly, the rise in power-specific fuel consumption caused by high ambient temperature decreases from 6.09% to 3.43%, reflecting a 2.66% improvement. An important finding of the study is that with inlet air cooling, the increase in GHG emissions reduces from 5.84% to 3.41%, signifying a 2.43% improvement on a hot day with a temperature of 55 °C.

Multicentric case series of scuba diving fatalities: The role of intracardiac gaseous carbon dioxide in the forensic diagnosis

Scuba diving fatalities post-mortem diagnosis presents a higher level of forensic complexity because of their occurrence in a non-natural human life environment. Scuba divers are equipped with diving gas to breathe underwater. It is essential for them to be fully trained in order to be able to manage their dive safely despite the varying increase of ambient pressure and temperature decrease. Throughout the dive, the inhaled diving gas is dissolved in the diver’s tissues during the descent and if the decompression steps are not respected during the ascent, the balance between the dissolved gas and the tissues (including blood) is disrupted, leading to a gaseous release in the organism. Depending on the magnitude of this gaseous release, free gas can occur in blood and tissue. Venous or arterial gas embolism can also occur as a consequence of decompression sickness or barotraumatism. It can also induce drowsiness that consequently leads to drowning. As a result, the occurrence of gas in dead scuba divers is very complex to interpret, as is the difficulty to distinguish it from resuscitation maneuver artifacts or body decomposition. Although the literature is scarce in this domain, significant work has been done to provide a precise intracadaveric gas sampling method to enlighten the cause and circumstances of death during the dive. The aim of this study is to obtain higher statistical significance by collecting a number of cases to confirm the gas sampling protocol and analysis and gain more information about the cause of death and the events surrounding the fatality through the establishment of clear management guidelines.

Energetic and exergetic analysis of a transcritical CO2 air-source heat pump water heating system in the cold region

To analyze the energetic and exergetic performance of the transcritical CO2 air-source heat pump water heating system in the cold region, the numerical model and simulation algorithm are set up and verified with the experiments. Under the low ambient temperature (−15 °C to 0 °C) and water inlet temperature (9 °C), the performance evaluation of the system is investigated using the developed numerical model at different compressor frequency (75, 80 and 85 Hz). The results show that Qgc, COP and ηex decrease by 14.47%, 12.78% and 20.83% respectively as the ambient temperature decreases from 0 °C to −15 °C. The CO2 outlet state of the gas cooler and corresponding slope of isotherms have significant effects on COP and ηex. The COPopt and ηex,opt exist in the system but at different compressor discharge pressures. With the compressor frequency increasing from 75 Hz to 85 Hz, the increase in Qgc is at the cost of a decrease in COP, and COPopt decreases by 5.31%. The effect of the compressor frequency on ηex is different as the compressor discharge pressure elevates. Thus, a suitable operating condition, considering different needs, should be selected in the system operation.

Effectiveness of hydrogen enrichment strategy for Wankel engines in unmanned aerial vehicle applications at various altitudes

This study investigates the effectiveness of the hydrogen-enrichment strategy on a Wankel engine for unmanned aerial vehicles (UAVs). The primary motivation behind this study is to contribute to the Wankel-type rotary engine designs by revealing the influences of the hydrogen enrichment method on the Wankel engine performance at various altitudes. To achieve these objectives, CFD simulations were conducted by applying a hydrogen enrichment method to a neat gasoline Wankel engine model at sea level, 5000 ft and 15,000 ft altitudes. The hydrogen energy fraction at the intake was gradually increased from 0% to 10%. The decrease in ambient air temperature, pressure, density, and insufficient fresh charge with the increase in altitude leads to the reduced reference chamber temperature and pressure of the Wankel engine. Thus, the combustion worsens, the heat release rate (HRR) and performance decrease, also emissions deteriorate in these colder operating conditions. On the other hand, the unique physicochemical properties of hydrogen such as wide flammability limits, high homogeneity, relatively small quenching distance and high flame speed allow hydrogen-enriched mixture flames to propagate toward the narrower gaps in the combustion chamber and make up for some drawbacks of Wankel engines. As a result, flame propagation is accelerated and fuel burning rate, peak pressure and temperature values in the reference chamber are increased by hydrogen addition. For the cases at sea level with 5% and 10% hydrogen energy fraction, IMEP is increased by 6.59%, 8.50%, and the indicated power is increased by 35.51% and 52.47%. In the cases with the same energy fraction at 15,000 ft, IMEP is increased by 26.61% and 48.75%, and the indicated power is reduced by 26.61% and 48.75%, respectively. It has been proven that a small amount of hydrogen by energy fraction improves combustion efficiency and performance. The findings show that hydrogen has excellent compatibility with Wankel engines and hydrogen enrichment is a very practical concept for the improvement of the performance of these engines for UAVs. Thus, Wankel engines, which are already a very favorable power source for UAVs, become even more favorable by the hydrogen-blending strategy.

Development of Binder for Fast-Charging for Li-Ion Battery

In the recent years, fast-charging is a battery technology that continues to be in demand for portable devices, electric vehicles and grid storage. Especially, fast charging capability has become one of the key features targeted by battery and EV industries. However, charging at high rates has been shown to accelerate degradation, causing both the capacity and power capability of batteries to deteriorate. In addition, the efficiency of fast charging depends on the materials and current in the battery, but also ambient temperature is emerging as an important issue. When the ambient temperature decreases, there is a decrease in performance and battery stability problems. This is the reason that the diffusion of Li-ion is slower in the electrodes and the electrolyte at low temperatures due to sluggish kinetics of interaction. Therefore, it is recommended to use low charging speed and voltage at low ambient temperature. In order to increase the fast charging efficiency, the material and battery design must be well designed, and among them, by improving the ionic conductivity of the binder, the resistance of the entire battery is lowered and the fast charging efficiency is improved. In addition, the resistance of material change at low temperature and its effect on fast-charging were also examined.

Design and development of an affordable and suitable rubber compounding for high altitude application up to −40 °C

The highest peak ever scaled by humans is Mount Everest at 8849 m. There is a constant decrease in pressure and a decrease in ambient temperature as one advance above sea level. Indian sub-continent has many places above 1500 m of spiritual importance. Variegated age group scale points of spiritual significance from children to the elderly. At such altitude there is a concern in breathing. Finding a hand-held portable breathing solution is therefore called for. This paper attempts to find an economical rubber-based polymer to be used as a material for a personal high-altitude lifesaving system up to −40 deg Celsius. Mechanical properties of different grades of rubber material with suitable fillers were investigated. Natural rubber with additives was compared with other rubber-based composites. The test samples were exposed to cryogenic conditions (-196 deg Celsius) by immersing in liquid Nitrogen for an appreciable time and were re-tested to exonerate the mechanical properties. Off all the tested samples, the best stiffness was exhibited by Butyl-Nitrile, which is 90% more than natural rubber. Similarly, after dipping in liquid Nitrogen, re-testing results confirm that the Butyl-Nitrile sample shows 95% higher stiffness than natural rubber. After being exposed to cryogenic conditions, the measured stiffness of samples is noted as more elevated than in normal conditions, attributed to its cross-linking properties. The cross-link bond of the butyl and nitrile rubber inhibits the motion inside it to increase the stiffness of the sample. The flow properties of samples were tested through a Mooney rheometer. The flow properties in cryogenic conditions were lower than in normal conditions. The article also delineates a design of the proposed breath assistance device and a wearable jacket.

A two-stage stochastic location–routing problem for electric vehicles fast charging

Electric cars are projected to become the vehicles of the future. A major barrier for their expansion is range anxiety stemming from the limited range a typical electric vehicle can travel. Electric vehicle batteries’ performance and capacity are affected by many factors. In particular, the decrease in ambient temperature below a certain threshold will adversely affect the battery’s efficiency. This paper develops a two-stage stochastic program model for charging stations’ optimal location to facilitate the routing decisions of delivery services that use electric vehicles while considering the variability inherent in climate and customer demand. A novel solution approach based on the progressive hedging algorithm is presented to solve the resulting mathematical model and to provide high-quality solutions within reasonable running times for problems with many scenarios. To evaluate the proposed formulation and solution approach’s performance, Fargo city in North Dakota is selected as a testbed. We observe that the location–routing decisions are susceptible to the electric vehicle logistics underlying climate, signifying that decision-makers of the direct current fast charging electric vehicle logistic network for cities that suffer from high-temperature fluctuations would not overlook the effect of climate to design and manage the respective logistic network efficiently.

Evolution and Parametric Analysis of Concrete Temperature Field Induced by Electric Heating Curing in Winter

Electric heat treatment is a widely used concrete curing method during the winter. Through direct and indirect heat exchange, the electric heating system tracks and controls the temperature of the heating medium based on a positive temperature coefficient (PTC) effect. In this study, to standardize the application of this treatment in the winter curing of concrete, the thermal energy conversion of an electric heating system and the heat-transfer characteristics of concrete have been studied. Based on the theoretical derivation, a calculation model of the relationship between the thermal energy of the electric heating system and the temperature of the concrete is established. The model is verified using the concrete heating and curing test results. The numerical analysis program COMSOL is used to analyze the effects of various factors on the concrete temperature field, including the electric heating power (e.g., the surface temperature of the electric heating system), concrete casting temperature, thermal conductivity, and heat release coefficient. The results show that decreasing the surface exothermic coefficient and increasing the heating temperature will significantly increase the peak temperature of the concrete. When the heat source temperature increases by 20 °C, the peak temperature could increase by approximately 13 °C. When the heating stops, the concrete volume increases temporarily, particularly in the region where the heating cable is buried. Consequently, an excessive heating power increase may cause cracks on the concrete surface. Compared with the factors of thermal conductivity and surface exothermic coefficient, the ambient temperature has the most significant effect on the concrete cooling rate when the heating stops. When the ambient temperature decreases by −20 °C, the cooling rate of concrete increases by 0.72 °C/h. The role of concrete insulation materials needs to be strengthened to reduce cooling rates during power outages and form removal. The findings from the study provide industry practitioners with a comprehensive guide regarding the specific applications of the electric heating system in early-age concrete curing.

Numerical study identifies the interaction between two adjacent dry cooling towers on fluid flow and heat transfer performances of the radiators at different points of each tower

A reliable thermal power plant in arid area usually has twin power-generating units equipped with two dry cooling towers. For a twin-tower configuration, a three-dimensional numerical model was built to capture thermo-hydraulic characteristics of both towers and distribution patterns of heat transfer performances of their radiators. Results showed that the interaction between two adjacent towers is a combination of negative blocking effect and positive wind-breaking effect of one tower to another, and its influences on radiators of different orientations are distinct and dependent on wind direction and speed. As wind attack angle increases, the overall cooling performance of the upstream tower improves and its sensibility to wind speed declines, while performance variation of the downstream tower shows a decrease followed by an increase. The downstream tower performs worse than the upstream tower in most crosswind cases, except for the wind situation where the downstream tower is almost entirely blocked by the upstream one. For a given wind speed of 12 m/s, cooling efficiency of the upstream (downstream) tower rises from 69.4% to 73.7% (91.7%) as wind attack angle varies from 0° to 90°, causing condenser pressure of the associated power unit to reduce from 23.5 kPa to 20.5 kPa (14.4 kPa). As the tower spacing increases, the tower interaction mitigates and cooling performance difference between the two towers narrows. The decrease of ambient temperature barely impacts cooling efficiency of the tower, but does cause a drop in condenser pressure of the unit without changing the sensitivity of condenser pressure to crosswind. The increase in condenser heat load helps to improve cooling tower performance and reduces its sensitivity to crosswind. Whereas, the growth in condenser heat load dominates the increases in condenser pressure and its sensitivity to crosswind.