Wet Bulb Research Articles

PERFORMANCE EVALUATION OF EXPERIMENTAL SOLAR EVAPORATIVE COOLING SYSTEMS

Evaporative cooling systems have many advantages over refrigeration systems, such as not necessarily requiring connection to the national grid, not using refrigerants that emit ozone-depleting substances into the environment, and can be constructed from locally available materials. However, little information on incorporating desiccant as an air preconditioning component to increase the performance of these coolers is available. In this regard, this study aimed to examine the efficacy of three cooling systems: an evaporative cooler with a silica gel desiccant component (desiccant cooler), an evaporative cooler without desiccant (desiccant-free cooler), and an evaporative charcoal cooler (charcoal cooler). Dry and wet bulb temperatures and relative humidity were recorded during the experiment and used to determine the cooling efficiencies of the systems; temperature drops; and humidity increases, which are used as performance indicators. Results demonstrate a significant (P<0.05) impact of the coolers on all analysed parameters. The desiccant cooler achieved the highest cooling efficiency at 87.2%, followed by the charcoal cooler at 79.3%, and the desiccant-free cooler at 67.2%. Temperature reduction was most pronounced in the desiccant cooler (3.7°C), followed by the charcoal cooler (3.2°C) and the desiccant-free cooler (2.8°C). Relative humidity levels increased by 30.7%, 23%, and 26.1% in the desiccant, desiccant-free, and charcoal coolers, respectively. Importantly, the evaporative cooler with desiccant operated without ozone-depleting refrigerants and utilized solar energy, offering an environmentally friendly solution. Its capacity to provide appropriate storage conditions for a wide range of fruits and vegetables makes it particularly beneficial for farmers lacking access to adequate cooling storage facilities, enabling them to preserve their produce effectively.

Using wet-bulb globe temperature meters to examine the effect of heat on various tennis court surfaces

In this study, we evaluated the thermal environments of different tennis courts using wet-bulb globe temperature (WBGT) meters. WBGT meters were installed in an outdoor hard court, sand-filled artificial grass court, and clay court (a softball field), and measurements were taken hourly from 9:00 to 17:00 on weekdays from June 1 to September 21, 2022. The results were compared with data from different courts and the nearest Japan Meteorological Agency station (JMA WBGT) based on the Japan Sports Association’s guidelines for exercise to prevent heat stroke. The median WBGT on each court was significantly higher for hard courts at the “Warning” (25 ≤ JMA WBGT < 28) level or above, sand-filled artificial grass courts at the “Severe Warning” (28 ≤ JMA WBGT < 31) level or above, and clay courts at the “Danger” (31 ≤ JMA WBGT) level than the JMA WBGT. Compared with the JMA WBGT, hard and sand-filled artificial grass courts are played on under particularly hot conditions. The results of this study could indicate to tournament organizers and coaches the importance of measuring the WBGT on each court surface from an early stage to prevent heat-related incidents.

Assessment of Heat Exposure and Health Outcomes in Rural Populations of Western Kenya by Using Wearable Devices: Observational Case Study.

Climate change increasingly impacts health, particularly of rural populations in sub-Saharan Africa due to their limited resources for adaptation. Understanding these impacts remains a challenge, as continuous monitoring of vital signs in such populations is limited. Wearable devices (wearables) present a viable approach to studying these impacts on human health in real time. The aim of this study was to assess the feasibility and effectiveness of consumer-grade wearables in measuring the health impacts of weather exposure on physiological responses (including activity, heart rate, body shell temperature, and sleep) of rural populations in western Kenya and to identify the health impacts associated with the weather exposures. We conducted an observational case study in western Kenya by utilizing wearables over a 3-week period to continuously monitor various health metrics such as step count, sleep patterns, heart rate, and body shell temperature. Additionally, a local weather station provided detailed data on environmental conditions such as rainfall and heat, with measurements taken every 15 minutes. Our cohort comprised 83 participants (42 women and 41 men), with an average age of 33 years. We observed a positive correlation between step count and maximum wet bulb globe temperature (estimate 0.06, SE 0.02; P=.008). Although there was a negative correlation between minimum nighttime temperatures and heat index with sleep duration, these were not statistically significant. No significant correlations were found in other applied models. A cautionary heat index level was recorded on 194 (95.1%) of 204 days. Heavy rainfall (>20 mm/day) occurred on 16 (7.8%) out of 204 days. Despite 10 (21%) out of 47 devices failing, data completeness was high for sleep and step count (mean 82.6%, SD 21.3% and mean 86.1%, SD 18.9%, respectively), but low for heart rate (mean 7%, SD 14%), with adult women showing significantly higher data completeness for heart rate than men (2-sided t test: P=.003; Mann-Whitney U test: P=.001). Body shell temperature data achieved 36.2% (SD 24.5%) completeness. Our study provides a nuanced understanding of the health impacts of weather exposures in rural Kenya. Our study's application of wearables reveals a significant correlation between physical activity levels and high temperature stress, contrasting with other studies suggesting decreased activity in hotter conditions. This discrepancy invites further investigation into the unique socioenvironmental dynamics at play, particularly in sub-Saharan African contexts. Moreover, the nonsignificant trends observed in sleep disruption due to heat expose the need for localized climate change mitigation strategies, considering the vital role of sleep in health. These findings emphasize the need for context-specific research to inform policy and practice in regions susceptible to the adverse health effects of climate change.

Heat, humidity and health impacts: how causal diagrams can help tell the complex story

The global health burden associated with exposure to heat is a grave concern and is projected to further increase under climate change. While physiological studies have demonstrated the role of humidity alongside temperature in exacerbating heat stress for humans, epidemiological findings remain conflicted. Understanding the intricate relationships between heat, humidity, and health outcomes is crucial to inform adaptation and drive increased global climate change mitigation efforts. This article introduces ‘directed acyclic graphs’ (DAGs) as causal models to elucidate the analytical complexity in observational epidemiological studies that focus on humid-heat-related health impacts. DAGs are employed to delineate implicit assumptions often overlooked in such studies, depicting humidity as a confounder, mediator, or an effect modifier. We also discuss complexities arising from using composite indices, such as wet-bulb temperature. DAGs representing the health impacts associated with wet-bulb temperature help to understand the limitations in separating the individual effect of humidity from the perceived effect of wet-bulb temperature on health. General examples for regression models corresponding to each of the causal assumptions are also discussed. Our goal is not to prioritize one causal model but to discuss the causal models suitable for representing humid-heat health impacts and highlight the implications of selecting one model over another. We anticipate that the article will pave the way for future quantitative studies on the topic and motivate researchers to explicitly characterize the assumptions underlying their models with DAGs, facilitating accurate interpretations of the findings. This methodology is applicable to similarly complex compound events.

Unravelling the impact of heat stress on daughter pregnancy rate in Mehsana buffalo through innovative breeding interventions

Heat stress profoundly affects the reproductive success of buffaloes, which are vital for the dairy industry due to their unique anatomical and physiological characteristics, necessitating careful evaluation under such conditions. Hence, this guided our search for quantifying heat stress' impact on Mehsana buffaloes using the best THI model and evaluating sires’ performance. Fertility records (days open converted to daughter pregnancy rate) were collected in the span of over 24 years, w.e.f. 1989 to 2012. Finally, 3070 records of first lactation cows, daughters of 117 sires from DURDA, Gujarat, India, were used in the analysis. Meteorological data were retrieved from IMD, Pune, to understand the relationship between daughter pregnancy rate (DPR) and heat stress indicators. Several heat stress models were compared based on R2, adjusted R2, AIC, and BIC values, and the impact of heat stress was quantified. The year was classified into different heat stress zones, viz., Non heat stress zone (NHSZ), Heat stress zone (HSZ), and critical heat stress zone (CHSZ), drawing from the findings of DPR and THI. The THI 4th model based on dry and wet bulb temperature was identified as the best-fit model, and DPR significantly changed (P < 0.01) by 1.14% per unit change in THI value based on the month of calving. The average EBVs of the sires for DPR were found to be 20.78% (NHSZ), 38.09% (HSZ), and 39.08% (CHSZ) using BLUP-SM and 20.78% (NHSZ), 37.30% (HSZ), and 38.87% (HSZ) using BLUP-AM. Subsequently, the optimum sire for each of the zones was prioritized. It is noteworthy that bulls that performed better in NHSZ did not perform as well in HSZ and CHSZ, and vice versa. This supports the possibility of evaluating bulls independently in each heat stress zone.

Experimental Study on the Performance of an Air Conditioning Unit with a Baffled Indirect Evaporative Cooler

Indirect evaporative coolers (IECs) use the latent heat of water evaporation to cool air. This system has the advantage of operating at low power without a compressor and does not increase the absolute humidity of the air. However, an IEC is difficult to use on its own because its cooling capacity is limited by the theoretical constraint of the wet-bulb temperature of the ambient air. Therefore, an air conditioning unit (ACU) was integrated with an IEC and experimentally evaluated in this study. The dry and wet channels of the IEC were integrated with an ACU evaporator and a condenser, unlike previous studies where IECs were integrated solely with either an evaporator or a condenser. This reduced the cooling load on the evaporator and helped the condenser to dissipate heat to improve the performance of the existing ACU. In addition, the IEC was equipped with baffles to improve its performance. To assess the extent of the performance improvement due to integration with the IEC, comparisons were also performed under the same experimental conditions with an ACU only. The results showed that under conditions with an indoor temperature of 32 °C, integrating the IEC with the ACU increased the average cooling capacity by 13.1% and decreased the average power consumption by 8.60% during the test period, compared to using only the ACU. Consequently, the average coefficient of performance (COP) increased by 19.5% compared to using only the ACU under the same conditions.

Optimizing energy efficiency in multi-chiller systems: A comprehensive Modelica-based approach

To achieve sustainable development of buildings, this paper investigates the energy-saving potential of multi-chiller systems by examining the interactions between sequencing optimization, load optimization, and parameter optimization in systems with varying capacities. A Modelica-based simulation platform, adaptable to various programming languages optimization engines, was developed for this purpose. The study introduces a sequencing optimization threshold function that considers both wet-bulb temperature and cooling load. Additionally, a two-stage optimization strategy that prioritizes parameter adjustments before sequencing is proposed. Case studies demonstrate that this threshold function and reversed optimization order can further enhance overall energy savings. Focusing on a system with three large chillers and one small chiller, the study reveals the energy benefits of activating the small chiller under specific conditions, improving overall system efficiency. The proposed optimization achieved a cumulative energy saving of 650,463 kWh over the summer, with sequencing contributing 5.64 %. Frequency conversion control of the water pump is identified as a significant energy-saving factor. This research provides a comprehensive approach to optimizing diverse chiller systems, highlighting substantial potential for energy conservation.

Vests with Radiative Cooling Materials to Improve Thermal Comfort of Outdoor Workers: An Experimental Study.

This study focuses on improving human thermal comfort in a high-temperature outdoor environment using vests with a radiative cooling coating. The effects of coating thickness on the radiative cooling performance were first evaluated, and an optimal thickness of 160 μm was achieved. Then, six subjects were recruited to evaluate the thermal comfort in two scenarios: wearing the vest with radiative cooling coatings, and wearing the standard vest. Compared with the standard vest, the coated vest decreases the maximum temperature at the vest inner surface and the outer surface by 5.54 °C and 4.37 °C, respectively. The results show that thermal comfort is improved by wearing radiative cooling vests. With an increase of wet bulb globe temperature (WBGT), the improving effects tend to decline. A significant improvement in human thermal comfort is observed at a WBGT of 26 °C. Specifically, the percentage of thermal sensation vote (TSV) wearing the cooling vest in the range of 0 to 1 increases from 29.2% to 66.7% compared with that of the untreated vest. At the same time, the average value of thermal comfort vote (TCV) increases from -0.5 to 0.2.

Sex differences in the association of long-term exposure to heat stress on kidney function in a large Taiwanese population study

The incidence and prevalence of dialysis in Taiwan are high compared to other regions. Consequently, mitigating chronic kidney disease (CKD) and the worsening of kidney function have emerged as critical healthcare priorities in Taiwan. Heat stress is known to be a significant risk factor for CKD and kidney function impairment. However, differences in the impact of heat stress between males and females remains unexplored. We conducted this retrospective cross-sectional analysis using data from the Taiwan Biobank (TWB), incorporating records of the wet bulb globe temperature (WBGT) during midday (11 AM–2 PM) and working hours (8 AM–5 PM) periods based on the participants’ residential address. Average 1-, 3-, and 5-year WBGT values prior to the survey year were calculated and analyzed using a geospatial artificial intelligence-based ensemble mixed spatial model, covering the period from 2010 to 2020. A total of 114,483 participants from the TWB were included in this study, of whom 35.9% were male and 1053 had impaired kidney function (defined as estimated glomerular filtration rate < 60 ml/min/1.73 m2). Multivariable analysis revealed that in the male participants, during the midday period, the 1-, 3-, and 5-year average WBGT values per 1 ℃ increase were significantly positively associated with eGFR < 60 ml/min/1.73 m2 (odds ratio [OR], 1.096, 95% confidence interval [CI] = 1.002–1.199, p = 0.044 for 1 year; OR, 1.093, 95% CI = 1.000–1.196, p = 0.005 for 3 years; OR, 1.094, 95% CI = 1.002–1.195, p = 0.045 for 5 years). However, significant associations were not found for the working hours period. In the female participants, during the midday period, the 1-, 3-, and 5-year average WBGT values per 1 ℃ increase were significantly negatively associated with eGFR < 60 ml/min/1.73 m2 (OR, 0.872, 95% CI = 0.778–0.976, p = 0.018 for 1 year; OR, 0.874, 95% CI = 0.780–0.978, p = 0.019 for 3 years; OR, 0.875, 95% CI = 0.784–0.977, p = 0.018 for 5 years). In addition, during the working hours period, the 1-, 3-, and 5-year average WBGT values per 1 ℃ increase were also significantly negatively associated with eGFR < 60 ml/min/1.73 m2 (OR, 0.856, 95% CI = 0.774–0.946, p = 0.002 for 1 year; OR, 0.856, 95% CI = 0.774–0.948, p = 0.003 for 3 years; OR, 0.853, 95% CI = 0.772–0.943, p = 0.002 for 5 years). In conclusion, our results revealed that increased WBGT was associated with impaired kidney function in males, whereas increased WBGT was associated with a protective effect against impaired kidney function in females. Further studies are needed to elucidate the exact mechanisms underlying these sex-specific differences.

Evaluation of radiation dose associated with underground uranium mining activities in east Singhbhum, Jharkhand, India

This paper presents the effect of ventilation parameters on the 222Rn inhalation dose in an underground uranium mine located in east Singhbhum of Jharkhand, India. This study reveals that the airflow rate variable statistically significantly predicts the 222Rn dose variable in the mine. On the other hand, no significant effect of other ventilation parameters such as barometric pressure, dry-bulb, and wet-bulb temperatures on 222Rn inhalation dose in the stopes was observed due to negligible variations in their values. Therefore, the airflow rate plays a significant role in reducing the effective radiation dose level in mines. In this study, the Equivalent Equilibrium Radon concentration (EER) and total effective radiation dose received by the miners involved in different mining activities in the various locations of the mine were found to be in ranges of 130–420 Bq m−3 and 0–3.17 mSv y−1, respectively. It also reveals that the miners involved in the stope preparation and timbering were exposed to more radiation than other mining activities. Under the existing ventilation conditions, the total effective radiation dose was far below the safe limit of 20 mSv y−1 recommended by the International Commission of Radiological Protection.

Association between wet-bulb globe temperature and kidney function in different geographic regions in a large Taiwanese population study.

The worldwide prevalence and incidence rates of end-stage renal disease have been increasing, and the trend is pronounced in Taiwan. This is especially evident in southern Taiwan, where the wet-bulb globe temperature (WBGT) is consistently higher than in other regions. The association between kidney function and WBGT has not been fully investigated. Therefore, the aim of this study was to evaluate the association between estimated glomerular filtration rate (eGFR) and WBGT and variations in this association across different geographic regions in Taiwan. We used the Taiwan Biobank (TWB) to obtain data on community-dwelling individuals, linked these data with WBGT data obtained from the Central Weather Bureau and then processed the data using a machine learning model. WBGT data were recorded during the working period of the day from 8:00 a.m. to 5:00 p.m. These data were then compiled as 1-year, 3-year and 5-year averages, recorded prior to the survey year of the TWB of each participant. We identified 114483 participants who had WBGT data during 2012-2020. Multivariable analysis showed that, in northern Taiwan, increases in 1- and 3-year averages of WBGT during the working period (β=-0.092, P=.043 and β=-0.193, P<.001, respectively) were significantly associated with low eGFR. In southern Taiwan, increases in 1-, 3- and 5-year averages of WBGT during the working period (β=-0.518, P<.001; β=-0.690, P<.001; and β=-0.386, P=.001, respectively) were gnificantly associated with low eGFR. These findings highlight the importance of heat protection for people working outdoors or in high-temperature environments as a measure to prevent negative impacts on kidney function. Moreover, we observed that in southern Taiwan, every 1°C increase in WBGT had a greater impact on the decrease in eGFR compared with other regions in Taiwan.

Farmworker-Relevant Heat Exposure in Different Crop and Shade Conditions

ABSTRACT Objectives Agricultural workers are at risk of heat-related illness, which is preventable. Few field studies have compared farmworker-relevant heat exposure in different conditions. We examined heat exposure over time in different potential shade and work locations to inform future occupational heat prevention approaches. Methods We assessed heat exposure in Eastern Washington State (WA) cherry and grape fields in August 2022. QUESTemp° monitors recorded Wet Bulb Globe Temperature (WBGT) and Black Globe Temperature (BGT) every 10 min from approximately 07:00–14:00 for three days in the center of crop rows (mid-row), under portable shade structures (shade), and in open field (open) locations. Linear mixed effects regression (LMER) models compared WBGT and BGT among field locations. Hourly time-weighted average WBGT and comparisons with occupational exposure limits (OELs) were computed for different hypothetical work-rest cycles during the hottest sampling hours, assuming different worker effort levels, rest locations (mid-row versus shade), and acclimatization statuses. Results Across all crops and locations during the study period, the mean/SD air temperature was 31°C (88°F)/3.9°C (6.9°F), with a maximum temperature of 39°C (102°F) and a mean/SD relative humidity of 30%/9.6%. LMER models suggested no significant difference in mid-row versus open WBGT but significantly lower WBGT in shade versus open locations for both cherries (main effect −5.14: 95% confidence interval [CI] −6.97,−3.32) and grapes (−6.20: 95%CI −7.73,−4.67), though this difference diminished over the course of the day. BGT was significantly higher in the mid-row than the shade (cherries main effect 14.33: 95%CI 9.52,19.13 and grapes 17.10: 95%CI 13.44,20.75). During the hottest sampling hour, the exceedances of OELs were reduced with assumptions of increased shaded break lengths, reduced effort level, and acclimatization. Conclusions Shade canopies, but not the crops studied, provided significant reductions in heat exposure. We observed increased protection from heat assuming longer shaded breaks and reduced effort levels. Results highlight the need for additional field research on the effectiveness, feasibility, and acceptability of different shade types and work-rest cycles to guide employer optimization of best practices for worker protections, including acclimatization before high heat, sufficient shaded rest time, reduced effort levels as the day warms, and avoiding work in peak heat.

Hybrid indirect and regenerative evaporative cooling design for enhanced cooling density

Indirect evaporative coolers (IEC) enable low-energy cooling of air without humidification. While a conventional IEC is limited to cooling incoming air down to its wet-bulb temperature, a regenerative IEC (M−cycle) can cool air further, approaching its dew point. In this study, a hybrid IEC-M−cycle design is proposed and evaluated for enhanced cooling, with initial cooling in the IEC portion, followed by subsequent cooling in the M−cycle section. Such a hybrid design produces the same product air temperature as a stand-alone M−cycle with 12–18 % lower heat transfer area. At a fixed system size, around 20 % higher cooling rate is achieved with the hybrid system while achieving the same product air temperature by optimizing the area fraction of the IEC section, and the recirculation flow rate. Overall, the proposed hybrid design enables improved indirect evaporative cooling at lower system sizes.

Understanding the influence of soil moisture on heatwave characteristics in the contiguous United States

In the context of global climate change, heatwaves are becoming increasingly significant because of the adverse impacts on human health and ecosystems. However, the quantification of heatwaves relies on different temperature metrics, and little is known about how the different types of heatwaves are affected by soil moisture. Using a set of observational datasets during the period 1981–2020, this study investigates the characteristics of warm-season heatwaves over the contiguous United States (CONUS) derived from three different temperature metrics (temperature, wet-bulb temperature, and equivalent temperature), and examines how different types of heatwaves are associated with soil moisture. Increasing trends of all types of heatwaves are observed in most parts of CONUS except for the central US, posing potential risks to human health. Due to limited evaporative cooling over dry soil, there is a substantial negative relationship between soil moisture and temperature-only heatwaves across the CONUS. Meanwhile, in some regions of the western and central CONUS, there is an evident positive relationship between soil moisture and humidity-included heatwaves, which represent the combined effects of temperature and humidity. The event-based analysis in Nebraska emphasizes that temperature-only heatwaves occur over relatively dry soil conditions, while humid heatwaves tend to occur over somewhat wet soil. Our results highlight the importance of considering different types of heatwaves and their relationship with soil moisture from the land-atmosphere coupling perspective, offering valuable insights for local and regional climate planning and mitigation.

The synergistic effect of high temperature and relative humidity on non-accidental deaths at different urbanization levels

Numerous studies have examined the impact of temperature on mortality, yet research on the combined effect of temperature and humidity on non-accidental deaths remains limited. This study investigates the synergistic impact of high temperature and humidity on non-accidental deaths in China, assessing the influence of urban development and urbanization level. Utilizing the distributed lag nonlinear model (DLNM) of quasi-Poisson regression, we analyzed the relationship between Wet Bulb Globe Temperature (WBGT) and non-accidental deaths in 30 Chinese cities from 2010 to 2016, including Guangzhou during 2012–2016. We stratified temperature and humidity across these cities to evaluate the influence of varying humidity levels on deaths under high temperatures. Then, we graded the duration of heat and humidity in these cities to assess the impact of deaths with different durations. Additionally, the cities were categorized based on gross domestic product (GDP), and a vulnerability index was calculated to examine the impact of urban development and urbanization level on non-accidental deaths. Our findings reveal a pronounced synergistic effect of high temperature and humidity on non-accidental deaths, particularly at elevated humidity levels. The synergies of high temperature and humidity are extremely complex. Moreover, the longer the duration of high temperature and humidity, the higher the risk of non-accidental death. Furthermore, areas with higher urbanization exhibited lower relative risks (RR) associated with the synergistic effects of heat and humidity. Consequently, it is imperative to focus on damp-heat related mortality among vulnerable populations in less developed regions.

Performance evaluation of an indirect-direct evaporative cooler using biomass-based packing material

ABSTRACT To overcome the drawbacks of a single-stage evaporative cooler, an indirect-direct type evaporative cooler was proposed and fabricated. An alternative arrangement of mild steel plates wherein unmixed heat transfer occurs between air and water to form an indirect evaporative cooler. This is followed by a packing arrangement made of biomass-based coconut coir that forms a direct evaporative cooler. Experiments were conducted by varying the air and water flow rates, and the performance of the coconut coir was compared with that of a commercially available celdek packing. Experimental results indicated that a combination of an indirect-direct evaporative cooler helped cool air without an appreciable increase in air-specific humidity. The performance of the coconut coir is slightly lower than that of the Celdek coir in terms of the drop in DBT and wet-bulb effectiveness. A maximum wet bulb effectiveness of 0.78 and 0.63 was achieved for the celdek and coconut coir packings, respectively. The maximum performance was attained at an air velocity of 6 m/s and a water flow rate of 3 LPM. Owing to the different advantages of coconut coir over celdek packings, it is recommended to use coconut coir as an alternative packing in indirect-direct evaporative coolers.

Uniformly elevated future heat stress in China driven by spatially heterogeneous water vapor changes

The wet bulb temperature (Tw) has gained considerable attention as a crucial indicator of heat-related health risks. Here we report south-to-north spatially heterogeneous trends of Tw in China over 1979-2018. We find that actual water vapor pressure (Ea) changes play a dominant role in determining the different trend of Tw in southern and northern China, which is attributed to the faster warming of high-latitude regions of East Asia as a response to climate change. This warming effect regulates large-scale atmospheric features and leads to extended impacts of the South Asia high (SAH) and the western Pacific subtropical high (WPSH) over southern China and to suppressed moisture transport. Attribution analysis using climate model simulations confirms these findings. We further find that the entire eastern China, that accommodates 94% of the country’s population, is likely to experience widespread and uniform elevated thermal stress the end of this century. Our findings highlight the necessity for development of adaptation measures in eastern China to avoid adverse impacts of heat stress, suggesting similar implications for other regions as well.

Utilizing Reversed Brayton Cycle for Enhanced Cooling Tower Technology

This study demonstrates an enhanced cooling tower technology (ECTT) under which the ambient air is precooled and dehumidified to improve the cooling tower efficiency. The reverse Brayton cycle, comprising a compressor, an air cooler, an expander, and a heat and mass exchanger, is used to precondition the ambient air before entering the cooling tower. A plant-scale thermodynamic model is constructed for ECTT, and the system parameters are optimized through genetic algorithm based on the maximum power gained from the system, including the effects of reducing the makeup water for the cooling tower. Compared to conventional cooling towers, the ECTT achieved sub-wet bulb cooling of water, which is 9.5 °C below the wet bulb temperature of ambient air, reduces steam condensation temperature by 34%, and increases steam turbine power output by 4.3%. It also reduces evaporative losses in the cooling tower and reduces the makeup water by 36%. With cooling tower exhaust recirculated in a closed loop, makeup water requirements are further reduced with additional gains in power output.

Numerical-experimental investigation of a wind tower-room sustainable system: A parametric analysis of the mixed convection with humidification

The wind tower is a sustainable architectural solution designed to improve natural ventilation and thermal comfort in buildings while reducing energy consumption. This study examines thermal comfort, natural ventilation, and heat transfer in a wind tower-room system with air humidification, such that the interaction of mixed convection with these parameters can be linked. The performance of the system is evaluated considering both natural and forced convection, influenced by differential heating and air inlet through the tower, respectively. A parametric analysis explores various parameters like outside air temperature, humidity, and velocity, along with room wall temperatures. Reynolds and Grashof numbers range from 8.57 × 103-1.99 × 105 and 2.20 × 109-1.31 × 1010, respectively. Simulations are validated against experimental data, with deviations under 5.0 %, 10.0 %, and 19.6 % for dry-bulb temperature, wet-bulb temperature, and air velocity. The system shows improved heat extraction efficiency under dominant forced convection conditions. Humidification yields PPD values between 10.0 % and 46.0 % and PMV values below 0 at air temperatures range 25.0–30.0 °C. At air temperatures of 35.0 °C with air humidity below 40.0 %, PPD values remain below 20.0 %. However, above 40 % humidity, humidification is less effective. The air exchange effectiveness reduction due to humidification is minimal at 0.61 %. These results illustrate the combination of parameters necessary for the optimal performance of the tower-room system, this study provides a valuable guide for integrating wind towers with humidification systems in building design and contributing to reduced electricity use and CO2 emissions.

Numerical Analysis on Performance Improvement of a Vertical Plate Indirect Evaporative Cooler with Baffles

The performance of the Plate Indirect Evaporative Cooler (PIEC) can be effectively improved by incorporating baffles in the dry channel. However, in the dimensional influence of the baffles on PIEC performance there remains a research gap. In order to investigate the impact of baffle dimensions on the wet bulb efficiency, namely the average heat transfer coefficient and the cooling capacity of the PIEC, this paper proposed and verified a three-dimensional numerical model and method based on the species transport model and the Euler wall film model. At the same time, in order to obtain the equilibrium point between the enhanced heat transfer performance and the additional resistance induced by baffles, a comprehensive performance evaluation index is introduced. The results indicate that, under the same conditions, (1) the baffle effect on PIEC performance is significant at a lower inlet air velocity, and the wet bulb efficiency of the PIEC with baffles can be improved by 22.8%; (2) the baffle effect on PIEC performance is negative if its relative length exceeds 60% or the primary air inlet velocity surpasses 4 m/s under the conditions specified in this paper; and (3) the baffle effect on PIEC performance is significant when its channel height is lower and its channel width is larger, and the wet bulb efficiency of the PIEC with baffles can be improved by 29.3%.