Design of A Smart Automotive Ventilation System For A Parked Car

Transcription

1 Design of A Smart Automotive Ventilation System For A Parked Car Gaurav Kumar Jaiswal 1, Mohit Gandhi 2, Sanket Phalgaonkar 3, Harshal Upadhyay 4, Ankit Agrawal 5, Vasudevan Rajamohan6, K.Ganesan 7 1,2,3,4,5,6 School of Mechanical and Building Sciences, VIT University, Tamil Nadu, India 7 TIFAC CORE in AUTOMATIVE INFOTRONICS, VIT University, Vellore, Tamil Nadu, India grvkjaiswal@gmail.com 1, mohitgaandhi@gmail.com 2, sanketphalgaonkar@ymail.com 3 harshal91upadhyay@gmail.com 4, ankitagrawal64@yahoo.com 5, vasudevan.r@vit.ac.in6, kganesan@vit.ac.in 7 Abstract The temperature inside a car can rise up to 30 o C more than the outside temperature and pose a serious threat for children or pets left in the car, when it is parked outside during summer. The increase in temperature of the car cabin is due to various modes of heat transfer such as conduction, convection and radiation. However, radiation along with the absorption is the main cause of this dramatic rise in temperature. This paper mainly focuses on regulating the internal temperature of the car. A new ventilation system has been designed that employs exhaust fan and blower, temperature sensors and electronic control circuitry to automatically control the temperature inside the car cabin under the constraint that ignition system is off. Experimental investigation is performed on a four wheeler vehicle parked under direct sun to observe temperature variation inside the car to understand the temperature difference between the inside and outside of the car. Furthermore, experiments were done on a prototype of a car-cabin, which was designed and fabricated based on the simulation performed using SOLIDWORKS. Two experiments were conducted with different ambient temperature and the targeted temperature at which the smart system should be activated. It was observed that the temperature inside the car dropped significantly when the smart ventilation system was on. Keywords- Automatic control, Parked car, Regulating temperature, Ventilation system. I. INTRODUCTION Generally in sub-continent countries like India where the temperature rises up to o C in summer, re-entering a car parked directly under the sun can be a difficult exercise owing to the drastic temperature rise inside the cabin. Even the air conditioning system takes some time to bring temperature back to desired level. Such drastic rise in temperature levels inside the cabin can be attributed to conduction (volume of air inside), convection (various metals and heat absorbing materials inside) and radiation (from the glass and body of the car). However, radiation is considered to be the most influencing factor in such heating [1]. The temperature variation inside the car depends on the thermal radiation exchanged between the environment and body of the car and also the radiation absorbed and emitted by the interiors of the cabin [2]. Various approaches have been adopted while addressing this problem. For example, an improved ventilator system that comprises of a high volumetric capacity fan and motor powered by solar panel was proposed by Saidur et al. [2]. A single blower has been used to control the temperature with help of external batteries [3]. Through-glass ventilation approach has been used where the fan assembly is supported on a window pane by cutting a hole in the glass window [4]. Our design employs an exhaust fan, a blower fan, a dedicated battery and a microcontroller based circuit. The microcontroller based circuit senses the temperature difference between inside and outside of the car, with the help of temperature sensors, and depending on the temperature difference switches the exhaust and blower fans on or off. To determine the specifications of the fans and their placement temperature variation of a car was observed, parked under direct sun, and flow simulation and analysis were performed on a SOLIDWORKS model of a car. After the simulation was completed experiment was performed on a prototype, fabricated based on the findings of the 83

2 simulation, to observe the performance of the smart ventilation system. A. Inside Temperature Variation In A MARUTI SUZUKI ALTO car The variation of temperature inside a car was studied by conducting a preliminary experiment on a MARUTI SUZUKI ALTO car using laboratory thermometers. The temperature variation inside the car was measured for 30 minutes and compared with those of ambient temperatures. The results are shown in Fig. 1. It can be seen that the temperature rises significantly in first 15 min and then remains constant at 71 o C after 20 min. It is concluded that significant variation in temperature was observed compared to the ambient temperature when the car was parked even for 30 minutes. simulation are as follows: Length =0.914m; Width =0.61 m; Height = 0.61 m; The model is considered to be made of mild steel with various material properties as follows: Density = 7850 kg/m 3 ; Young s modulus =210 GPa; Thermal conductivity = 173 W/mK; Coefficient of thermal expansion = ; Specific heat capacity = 1765 J/kgK; Poisson ratio= 0.3; Dimensions of the ducts used are 0.011m X 0.011m. The flow distribution and the temperature variation were studied for various feasible cases such as: 1) Two ducts placed directly opposite to each other at the two sides of the car 2) Two ducts placed adjacent to each other on the same side of the car 3) Two ducts placed diagonally opposite to each other. The results of the flow analysis for the various cases are shown in Figs. 2 to 4. It can be observed from Fig. 2 that the flow distribution could not be effectively achieved inside the car when the two ducts were placed opposite to each other. This is due to the fact that the exhaust fan would directly suck the air flow that is flowing through the ventilation duct. Fig.1 Temperature inside and outside the car B. Design and flow analysis of the test rig The positions of the two ducts (one for exhaust fan and another for blower) at the sides of the prototype car model used for the experimental investigation, are identified by performing a simulation on a model of car (Fig. 2) using FLOWEXPRESS in SOLIDWORKS. The various dimensions of the car model considered in. Fig.2 Velocity profile of air with ducts placed directly opposite to each other a) Isometric view b ) Top view Fig.3 Velocity profile of air when ducts are on same side 84

3 a) Isometric view b) Top view Fig.4 Velocity profile of air when ducts are diagonally opposite side. The simulation is performed on the car model with the ducts, for exhaust and blower fans, placed at the same side of the car model and the results are shown in Fig. 3(a) and (b). It can be realized that better distribution of airflow is achieved compared to the case where the ducts are placed directly opposite to each other. However, a dead zone is observed (Fig. 3 (b)) where the airflow is very minimal and, hence this configuration was not selected for our experiment. all point goals seem to converge to a steady state after 245 s. Hence, it is concluded that design with the ducts placed diagonally provides effective heat transfer to the surroundings and reduces the inside temperature effectively. Hence the model with ducts placed diagonally has been considered as the benchmark for the experimental investigation. The simulation is also performed on the car model considering the exhaust and the blower ducts placed diagonally opposite to each other and the flow analysis results are shown in Fig. 4(a) and (b). It can be realized that better distribution of airflow is achieved compared to both cases where the ducts are placed opposite with each other and on the same side. Furthermore the nonexistence of the dead zone is observed. Hence, it is concluded that the air flow could be distributed effectively inside the car when the ducts are placed diagonally opposite to each other. The variation of temperature with time is also investigated theoretically by considering the ambient and inside temperatures as 308 K and 328 K, respectively. The simulated temperature variation at four locations at a volume air flow rate of 42 cfm, for exhaust and blower fans, is shown in Fig. 5. (a) Position of various point goals(sensors) Placement of sensors has been done as shown in Fig. 5 (a): point goals 1 and 2 represent the temperature sensors that have been placed near exhaust and blower fans while point goals 3 and 4 represent sensors which have been placed in areas with relatively lesser air-flow. It can be seen in the results (Fig. 5 (b)) that the temperature decreases at a higher rate initially at point goals 1 and 2 as compared to 3 and 4, since they are placed nearer to the fans. However, temperatures at (a) Temperature at various point goals Fig.5 Temperature variation of various points inside the car 85

4 II. EXPERIMENTAL SETUP A. Fabrication of the prototype 8 and 9 show the block diagram of the electronic setup used and the logic used for the programming. The components used in the ECU are shown in Fig.10. LM-35 temperature sensors (1 and 2) were used to observe the inside and outside temperatures. ATMEGA 16 microcontroller (3) was used as the main control unit and AT24C512 memory log (4) was used for recording the data. AT IRF640 Mosfets (5) were used for controlling the speed (RPM) of the fans. Fig. 6 Prototype model of the car used for experimental investigation The experimental investigation is performed on a prototype model of car (Fig. 6) with various dimensions and material properties as mentioned in previous section. The blower and the exhaust fans are fitted at the locations of the ducts as identified in the simulation (Fig. 7). Fig. 8 Block diagram of the electronic control circuit (ECU) Fig. 7 Position of the ducts The temperature sensors are fixed at five different locations as identified by simulation (Fig. 5 (a)) for inside sensors and one sensor is placed on the car (outside) to measure the ambient temperature. A microcontroller based program is developed in such a way that, when the difference between the average temperatures of the four sensors located inside the car and the ambient temperature of the car exceeds a specified value; both the exhaust fan and the blower would be powered on using the batteries. Then both the fans would run for a given time (based on the ambient temperature), and then again the temperature difference, T av-a, would be checked and if it falls below the desired value then the fans would be switched off and the cycle would continue until the ignition system is started. Figs. Fig.9 Block diagram used for the programming by microcontroller Fig.10 Electronic circuit and the components used 86

5 B. Experimental Investigation The experiments were performed on two different ambient conditions, one with ambient temperature of 33⁰C and other with that of 39⁰C. Furthermore, the average temperature of the four sensors located inside the car and the ambient temperature (T an-a ) was set as 8⁰C and 15⁰C, respectively. On the second day testing the prototype model (Fig. 13) was coated with black paint to enhance the heat absorption. be seen that the smart ventilation system provides much reduction in temperature once the smart ventilation was activated. Similar experiments were conducted by setting the temperature difference, T av-a, as 15⁰C and the ambient temperature as 39⁰C (Fig. 13) and the results, thus obtained, are shown in Fig. 14. Fig. 13 Day 2 testing (with black coating) on a normal sunny day Similar observations were observed as those with the previous case which shows the effectiveness of the smart ventilation system on reducing the temperature inside the car at any desired level. Fig. 11 Day 1 testing (without black coating) on a mildly sunny day During the first test (Fig. 11), when the temperature difference, T av-a, reached the target temperature of 8⁰C, the blower was started automatically 30 sec after the exhaust fan was started. The temperatures were also measured at the four locations when the smart ventilation system was not incorporated. The drop in temperature inside the car was observed with and without using the smart ventilation system and the results are shown in Fig. 12. Fig.14 Temperature variation inside the prototype on hot sunny day Fig.12 Temperature variation inside the prototype on a mildly sunny day It was noticed that the smart ventilation was switched off once the temperature difference, T av-a, reached the targeted difference and then the system was restarted automatically once the temperature difference increased above the targeted temperature. It can hence III. CONCLUSION A new ventilation system aimed at regulating temperature inside a parked car was designed that employs exhaust fan and blower, temperature sensors and electronic control circuitry, under the constraint that ignition system is off. Experimental investigations were done on a prototype of a car-cabin, which was designed and fabricated based on the simulation performed using SOLIDWORKS. It was observed that the temperature inside the car dropped significantly when the smart ventilation system was powered on. Considering the experimental results and data from the simulation, the target of cooling the fabricated cabin in the ambient conditions within a conditioned time was achieved. 87

6 IV. ACKNOWLEDGMENT We are grateful to Mr. Mohan Prabhu, Senior Technician, TIFAC CORE in Automotive Infotronics, VIT University, for helping us with the ECU design aspect of our project and Mr. Venkata Krishnan, Advanced Technical leader, Delphi Technical Centre, Bangalore for giving us valuable insights about the industrial aspects and feasibility of our project and research paper. We would also like to extend our heartfelt gratitude to our colleague Suraj Swaminathan, School of Electronics Engineering, VIT University. V. REFERENCES [1] Ibrahim Almanjahie, Temperature Variation in a Parked Car, 2008 [2] R. Saidur, H. H. Masjuki and M. Hasanuzzaman, Performance of an Improved Solar Car Ventilator, International Journal of Mechanical and Materials Engineering (IJMME), Vol. 4 (2009), No. 1, [3] Antonio Martin Galvez-Ramos, Climate control system for parked automobiles, Patent Application Number , [4] Michael J. Lesle and Paul J. Kolokowski, Through Glass Ventilation,