On the Use of Wearable Face and Neck Cooling Fans to Improve Occupant Thermal Comfort in Warm Indoor Environments

Face and neck cooling has been found effective in improving thermal comfort during exercise in the heat despite the fact that the surface area of human face and neck regions accounts for only 5.5% of the entire body. Presently very little documented research has been conducted to investigate cooling the face and neck only to improve indoor thermal comfort. In this study, two highly energy efficient wearable face and neck cooling fans were used to improve occupant thermal comfort in two warm indoor conditions (30 and 32 °C). Local skin temperatures and perceptual responses while using the two wearable cooling fans were examined and compared. Results showed that both cooling fans could significantly reduce local skin temperatures at the forehead, face and neck regions by up to 2.1 °C. Local thermal sensation votes at the face and neck were decreased by 0.82–1.21 scale unit at the two studied temperatures. Overall TSVs decreased by 1.03–1.14 and 1.34–1.66 scale units at 30 and 32 °C temperatures, respectively. Both cooling fans could raise the acceptable HVAC temperature setpoint to 32.0 °C, resulting in a 45.7% energy saving over the baseline HVAC setpoint of 24.5 °C. Furthermore, occupants are advised to use the free-control cooling mode when using those two types of wearable cooling fans to improve thermal comfort. Finally, despite some issues on dry eyes and dry lips associated with those wearable cooling fans, it is concluded that those two highly energy-efficient wearable cooling fans could greatly improve thermal comfort and save HVAC energy.

Low-Cost Air-Cooling System Optimization on Battery Pack of Electric Vehicle

Temperature management for battery packs installed in electric vehicles is crucial to ensure that the battery works properly. For lithium-ion battery cells, the optimal operating temperature is in the range of 25 to 40 °C with a maximum temperature difference among battery cells of 5 °C. This work aimed to optimize lithium-ion battery packing design for electric vehicles to meet the optimal operating temperature using an air-cooling system by modifying the number of cooling fans and the inlet air temperature. A numerical model of 74 V and 2.31 kWh battery packing was simulated using the lattice Boltzmann method. The results showed that the temperature difference between the battery cells decreased with the increasing number of cooling fans; likewise, the mean temperature inside the battery pack decreased with the decreasing inlet air temperature. The optimization showed that the configuration of three cooling fans with 25 °C inlet air temperature gave the best performance with low power required. Even though the maximum temperature difference was still 15 °C, the configuration kept all battery cells inside the optimum temperature range. This finding is helpful to develop a standardized battery packing module and for engineers in designing low-cost battery packing for electric vehicles.

On the use of facial and neck cooling to improve indoor occupant thermal comfort in warm conditions

Face and neck cooling has been found effective to improve thermal comfort during exercise in the heat despite the surface area of human face and neck regions accounts for only 5.5% of the entire body. Presently, very limited work in the literature has been reported on face and neck cooling to improve indoor thermal comfort. In this work, two energy-efficient wearable face and neck cooling fans were used to enhance occupant thermal comfort in two warm indoor conditions (30 & 32 °C). Local skin temperatures and perceptual responses while using those two wearable cooling fans were examined and compared. Results showed that both cooling fans could largely reduce local skin temperatures at the forehead, face and neck regions up to 2.1 °C. Local thermal sensation votes at the face and neck were decreased by 0.82-1.21 scale unit at two studied temperatures. Overall TSVs dropped by 1.03-1.14 and 1.34-1.66 scale unit at 30 and 32 °C temperatures, respectively. Both cooling fans could extend the acceptable HVAC temperature setpoint to 32.0 °C, resulting in an average energy saving of 45.7% as compared to the baseline HVAC setpoint of 24.5 °C. Further, the free-control cooling mode is recommended to occupants for further improving thermal comfort while using those two types of wearable cooling fans indoors. Lastly, it is concluded that those two wearable cooling fans could greatly improve thermal comfort and save HVAC energy despite some issues on dry eyes and dry lips associated with those wearable cooling fans were noted.

Insights Into The Effect of Shelter Modification On Key Biochemical Aspects vis-a-vis the Performance of Sahiwal Zebu Cows Reared in Hot Arid Ambience

This study was undertaken to evaluate the effect of shelter modifications in the form of floor alteration and heat stress amelioration aids on the biochemical aspects and productive performance of Sahiwal zebu cows. 24 healthy Sahiwal cows in their second or third parity were randomly assigned to four groups (G1, G2, G3, and G4) having 6 cows each and were studied for duration of 150 days from June to November. G1 acted as control without any shelter modification, while G2 cows were housed in stalls with rubber mat covered floors, G3 cows were provided with cooling fans along with water sprinkling twice a day, and G4 cows were housed in stalls combining rubber mat floors with cooling fans and water sprinkling twice a day. This study revealed a significant (p<0.05) effect of shelter modification on milk yield, though no significant effect on milk composition was found. Among blood biochemical parameters, serum cholesterol and cortisol levels registered a significant (p<0.05) effect of shelter modification. The use of heat amelioration aids with, and without rubber mat floors positively influenced the productive and biochemical aspects of Sahiwal cows. Such strategies can be utilized to reduce stress on animals and help in maintaining their production.

Noise Characteristics of Automobile Cooling Fan Based on Circumferential Mode Analysis

The fan is the main component of the cooling system of an automobile engine. A typical automobile cooling fan consists of a shrouded axial fan, stator vanes, a deflector, and a cover. With recent developments in the automobile industry, the increase in the speed of rotation and blade load of cooling fans has increased the noise generated by them. To reduce it, it is important to analyze the characteristics of this noise. This paper uses an acoustic test to examine the characteristics of flow and noise of automobile cooling fans. The frequency spectrum and far-field radiation of the noise of the fan are first analyzed through far-field measurements, and the influence of the single rotor, tip clearance of the blade, and cover on fan noise is studied. The distribution of the mode spectrum and characteristics of sound propagation of discrete tonal noise are then examined using the circumferential mode test. The influence of the flow structure on fan noise is also studied. The flow characteristics and distribution of the source of noise of the automobile cooling fan are then used to analyze the influence of the structure of the fan on the noise generated by it. The results can help develop designs to reduce the noise of automobile cooling fans.

Noise Characteristics of Automobile Cooling Fan Based On Circumferential Mode Analysis

The fan is the main component of the cooling system of an automobile engine. A typical automobile cooling fan consists of a shrouded axial fan, stator vanes, a deflector, and a cover. With recent developments in the automobile industry, the increase in the speed of rotation and blade load of cooling fans has increased the noise generated by them. To reduce it, it is important to analyze the characteristics of this noise. This paper uses an acoustic test to examine the characteristics of flow and noise of automobile cooling fans. The frequency spectrum and far-field radiation of the noise of the fan are first analyzed through far-field measurements, and the influence of the single rotor, tip clearance of the blade, and cover on fan noise is studied. The distribution of the mode spectrum and characteristics of sound propagation of discrete tonal noise are then examined using the circumferential mode test. The influence of the flow structure on fan noise is also studied. The flow characteristics and distribution of the source of noise of the automobile cooling fan are then used to analyze the influence of the structure of the fan on the noise generated by it. The results can help develop designs to reduce the noise of automobile cooling fans.

Design Considerations and Selection of Cost-Effective Switched Reluctance Drive for Radiator Cooling Fans

Switched reluctance motors (SRMs) are simple in structure, easy to manufacture, magnet-less, brushless, and highly robust compared to other AC motors which makes them a good option for applications that operate in harsh environment. However, the motor has non-linear magnetic characteristics, and it comes with various pole-phase combinations and circuit topologies that causes many difficulties in deciding on which type to choose. In this paper, the viability of SRM as a low-cost, rugged machine for vehicle radiator cooling fan is considered. First, necessary design considerations are presented, then three commonly use types of SRM are analyzed: A 3-phase 6/4, 3-phase 12/8, and a 4-phase 8/6 to find their static and dynamic characteristics so the most suitable type can be selected. Simulation results show that the 8/6 SRM produces the highest efficiency with less phase current which reduces the converter burden. However, with asymmetric half bridge converter, eight power switches are required for 8/6 SRM and thus put a burden on the overall drive cost. As a solution, the Miller converter with only six switches for four phase SRM. To verify the proposed idea, the 8/6 SRM was manufactured and tested. The results show that Miller converter can be used for the proposed SRM with slightly reduced efficiency at 80.4%.

The Effect of Blade Count on Body Force Model Performance for Axial Fans

Body force models enable inexpensive numerical simulations of turbomachinery. The approach replaces the blades with sources of momentum/energy. Such models capture a “smeared out” version of the blades' effect on the flow, reducing computational cost. The body force model used in this paper has been widely used in aircraft engine applications. Its implementation for low speed, low solidity (few blades) turbomachines, such as automotive cooling fans, enables predictions of cooling flows and component temperatures without calibrated fan curves. Automotive cooling fans tend to have less than 10 blades, which is approximately 50% of blade counts for modern jet engine fans. The effect this has on the body force model predictions is unknown and the objective of this paper is to quantify how varying blade count affects the accuracy of the predictions for both uniform and non-uniform inflow. The key findings are that reductions in blade metal blockage combined with spanwise flow redistribution drives the body force model to more accurately predict work coefficient as the blade count decreases, and that reducing the number of blades is found to have negligible impacts on upstream influence and distortion transfer in non-uniform inflow until extremely low blade counts (such as 2) are applied.