MICRO HEAT PIPE SYSTEM FOR SPACE AVIONICS

Transcription

1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 2, February 2018, pp Article ID: IJMET_09_02_060 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed MICRO HEAT PIPE SYSTEM FOR SPACE AVIONICS S. Mahendran Assistant Professor, School of Aeronautical Sciences, Hindustan Institute of Technology & Science V. Paulson Assistant Professor, School of Aeronautical Sciences, Hindustan Institute of Technology & Science Stanley Samlal Assistant Professor, School of Aeronautical Sciences, Hindustan Institute of Technology & Science Pratik Narangikar M.Tech Avionics, School of Aeronautical Sciences, Hindustan Institute of Technology & Science ABSTRACT This paper presents an experimental analysis of a Local Thermal Control System for Avionics systems inside a spacecraft. For the space missions, temperature control of the electronics onboard plays a very important role in the proper functioning of the spacecraft. Current technologies used for this purpose are Multilayer Insulation (MLI), Shutters and Fluid Loops. This project aims at maintaining operating temperature of electronic equipment used in spacecraft at an individual level. It utilizes Heat Pipes as a means of heat transfer, thereby providing cooling operation and micro heaters for heating operation. Working at the local level, this system accesses the hotspots and in event of a rise in ambient temperature, it transfers heat with help of heat pipes to the cooling system and keeps the temperature low. Similarly, when there is a drop in ambient temperature, this system uses thermal cutoff mechanism to turn a micro heater ON, which helps in avoiding freezing temperatures. It will be able to access the hotspots which are the primary targets, both for the heating as well as the cooling operation. This system will greatly reduce the reliance on Thermal ControlSystem of spacecraft and will ensure proper functioning of all electronics even if there is a rise or fall in temperature of the spacecraft. Keywords: micro heat pipe, space avionics, thermal control editor@iaeme.com

2 S. Mahendran, V. Paulson, Stanley Samlal and Pratik Narangikar Cite this Article: S. Mahendran, V. Paulson, Stanley Samlal and Pratik Narangikar, Micro Heat Pipe System for Space Avionics, International Journal of Mechanical Engineering and Technology 9(2), pp INTRODUCTION Thermal Control Systems perform the function of maintaining the temperature inside the spacecraft within permissible levels. Thermal Control Systems are classified as Active Thermal Control Systems and Passive Thermal Control System based upon their working mechanism. Active Thermal Control System uses fluid loops, thermoelectric coolers and heaters. Fluid Loops contain a fluid with good heat absorbing capability pumped through loops of pipes and distribute heat throughout the spacecraft. Passive Thermal Control System technologies include Multilayer Insulations (MLI), louvres/shutters and Fluid Loops. Active Thermal Control System is used when the heat absorption provided by Passive Thermal Control System is insufficient. Multilayer Insulation is done by applying coatings of insulating materials over the surface of spacecraft, thereby avoiding the heat transfer. Shutters are used on the side of spacecraft that is exposed to Sun, so as not to allow the heat inside and keep the temperature low. Fluid Loops consist of liquid flowing through pipes that carry heat from the hotter areas of spacecraft to the cooler areas, thereby maintaining the temperatures. All of the systems used currently provide centralized effects, and focus mainly on the ambient temperature if the temperature inside the spacecraft starts rising or falling. The temperature of the electronic systems is then regulated according to the ambient temperature. In case the ambient temperature inside the spacecraft goes beyond the operating limits, the electronic components will start malfunctioning. In order to avoid this, a system has been developed wherein Local Thermal Control System will be provided to every electronic component so that in event of a rise or fall in ambient temperature beyond the operating limits, the temperature of electronic components can be kept in check and all functions of spacecraft performed satisfactorily. In this system, Sun sensors used inside spacecraft are taken into consideration. Sun sensors are used inside spacecraft to detect the position of the Sun. It helps during attitude control and navigation. Besides spacecraft, Sun sensors are also used in Solar Arrays, Suntracking systems and weather forecasting stations. The operating temperature range for the Sun sensor is -30 C to +50 C. The primary objective is to keep the temperature of this sensor within the -30 C to +50 C range. Whenever the temperature starts rising above +50 C, the heat pipes transfer heat from the sensors towards the central cooling system of the spacecraft. When the temperature starts reducing below a threshold temperature value, a micro heater is turned ON via a thermal switch that keeps the temperature of the sensor much above the lower extreme temperature of -30 C. The various components that have been used in this system include an Aluminium Block (to emulate the sensor), a 50 W soldering iron to provide the heating effect, heat pipes (Copper-Acetone, Copper-Ethanol and Stainless Steel-Acetone), a thermal cut-off switch, a 2- way switch (to switch control between Digital Temperature Controller and thermal cut-off switch), a Digital Temperature Controller, a thermocouple and two indicator lamps. This paper aims to learn about the performance of the Thermal Control System in controlling the temperature of the sensor. For this purpose, the ambient temperature is maintained at 25 C, which is the ambient temperature inside spacecraft, and the Aluminium Block is heated with a constant output of 50W and the temperature of the block is maintained at 60 C. This is done in order to simulate the condition of heating up of sensors due to its heat output under normal conditions. The temperature of the condenser end of heat pipes is editor@iaeme.com

3 Micro Heat Pipe System for Space Avionics observed to understand the heat transfer due to heat pipes leading to reduction of temperature of the sensor. Similartest is performed maintaining the ambient temperature at 50 C, and the temperature variation of condenser end of heat pipes is observed again. This helps to understand the heat transfer of heat pipes under threshold conditions. This condition is tested with different combinations of heat pipe & working fluid and the performances compared to each other. After this, the setup is subjected to extremely low temperatures of -30 C, and the temperature of Aluminium Block observed over a period of time. This ensures the successful operation of the setup even under freezing temperatures. The temperature profiles of the system will be observed and the results recorded in tabulated form. HEAT PIPE OPERATION AGAINST GRAVITY The heat pipe will be arranged as per the following configuration to enable operation against gravity. Figure 1 Heat pipe Configuration for operation against gravity [5] The evaporator section is kept in contact with the sensor in the above configuration. The evaporator absorbs the heatand the liquid gets pushed towards the condenser end due to vapour pressure. Here the liquid condenses and travels back to the evaporator end via the mesh on the inner walls of the heat pipe. The paper is organised as follows. Section II describes the components of the setup. Section III explains the procedure of the experimentation. Section IV gives the results and a comparative analysis of the different heat pipe-working fluid combinations. Section V summarises the conclusion from this study editor@iaeme.com

4 2. COMPONENTS S. Mahendran, V. Paulson, Stanley Samlal and Pratik Narangikar Figure 2 Project setup testing with Aluminium block and plate inside the environmental chamber a) Aluminium Block- This block is used to imitate the differences in temperature that the Sun sensor undergoes with variation in ambient temperature inside the spacecraft and under the influence of the cooling and heating effects due to heat pipes and heater respectively. b) 50 W soldering iron - The soldering iron is used to imitate the rise in temperature of the Sun sensor due to its internal heating. It alsoserves the dual purpose of heating when the ambient temperature drops below freezing temperatures. c) Heat pipes- Heat pipesperform the function of transferring heat from the Aluminium block towards the condenser end. The flow of liquid from the condenser end back to the evaporator end is aided by the mesh on the inner walls of the heat pipe. Mesh is made up of sintered powder or wire mesh. Partial vacuum is maintained inside these heat pipes. Three combinations of heat pipes with variations in material and working fluids have been used; Copper - Acetone, Copper - Ethanol and Stainless Steel Acetone. d) Thermal cut-off switch (KSD301) - KSD301 thermostat is NC type which has a threshold temperature of 10 C. It is used to switch the heater ON when the temperature starts dropping below 10 C. As long as the temperature is above 10 C, KSD301 is in NO position and switches over when the temperature drops below 10 C, turning the heater ON. Figure 3 Thermal Switch (KSD301) editor@iaeme.com

5 Micro Heat Pipe System for Space Avionics a) 2-way switch - 2-way switch is used to switch heating operation control between the Digital Temperature Controller and the KSD301 thermostat. b) Digital Temperature Controller (AI-5741) - This temperature controller is usedto control heating of the Aluminium Block and maintain the temperature of the block at the desired value. Once a set point has been fixed, the controller performs successive switching ON and OFF to maintain the temperature of the block at the set point temperature. c) Thermocouple - A J-type thermocouple has been used to sense the temperature of the block during the entire test. This thermocouple is connected to the Digital Temperature Controller which senses the temperature and performs switching operation accordingly. d) Indicator lamps - Two red panel mount type indicator lamps have been used in order to indicate that the Digital Temperature Controller and the KSD301 thermostat have been switched ON. e) 230V AC to 5V DC converter - This converter is used to provide the 5V DC supply needed to operate the cooling fan. 3. EXPERIMENTATION Figure 4 Project setup arranged for testing Figure 5 Project setup testing with Aluminium block and plate inside the environmental chamber editor@iaeme.com

6 S. Mahendran, V. Paulson, Stanley Samlal and Pratik Narangikar The test setup has been arranged as shown in the picture. The main objective of the test is to observe whether the system maintains its temperature in the operating temperature range i.e. -30 C to +50 C even if there is a rise or fall in ambient temperature. The heat pipes have the material-working fluid combinations of Copper-Acetone, Copper- Ethanol and Stainless Steel-Acetone respectively. The Digital Temperature Controller set point was fixed at 60 C. The thermocouple is fixed in the Aluminium Block as shown in the picture. The heat pipes were provided with a fan to create the cooling effect. The fan is provided with a 5V DC supply. The test was performed in four phases: a. Aluminium Block is fitted with Copper-Acetone heat pipes. Ambient temperature is set at 25 C. Temperature of Aluminium Block is maintained at 60 C and temperature of condenser end of Heat pipes (near cooling fan) is observed over a period of 30 minutes. Again same setup is maintained at ambienttemperature of 50 C and Aluminium Block temperature of 60 C and temperature of condenser end of heat pipes observed over a period of 30 minutes. b. Aluminium Block is fitted with Copper-Ethanol heat pipes. Ambient temperature is set at 25 C. Temperature of Aluminium Block is maintained at 60 C and temperature of condenser end of Heat pipes (near cooling fan) is observed over a period of 30 minutes. Again same setup is maintained at ambient temperature of 50 C and Aluminium Block temperature of 60 C and temperature of condenser end of heat pipes observed over a period of 30 minutes. c. Aluminium Block is fitted with Stainless Steel-Acetone heat pipes. Ambient temperature is set at 25 C. Temperature of Aluminium Block is maintained at 60 C and temperature of condenser end of Heat pipes (near cooling fan) is observed over a period of 30 minutes. Again same setup is maintained at ambient temperature of 50 C and Aluminium Block temperature of 60 C and temperature of condenser end of heat pipes observed over a period of 30 minutes. d. An environmental chamber is set to precool till -30 C and the setup is then placed inside the chamber. Temperature variation of the Aluminium Block is observed for a period of 60 minutes. The collected results are tabulated and compared for performance of the heat pipes for cooling operation and the heater for heating operation. 4. RESULTS AND COMPARATIVE ANALYSIS Figure 6 Phase 1: Copper-Acetone heat pipes editor@iaeme.com

7 Micro Heat Pipe System for Space Avionics During phase 1A, the setup contains Copper and Acetone heat pipes and shows satisfactory operation at ambient temperature of 25 C. During phase 1B, the temperature is brought down to 52 C which is very near to the operating limit temperature. Figure 7 Graph for Phase 1A: Copper-Acetone heat pipes Above graph shows the temperature variation of the aluminium block with the Copper- Acetone heat pipes over a period of 30 minutes at ambient temperature of 25 C. Blue line indicates the temperature of Aluminium block and the orange line indicates the temperature variation of the heat pipes. The temperature of the heat pipes attains amaximum value of 32.1 C which is well below the operating temperature range. Figure 8 Graph for Phase 1B: Copper-Acetone heat pipes Above graph shows the temperature variation of the aluminium block with the Copper- Acetone heat pipes over a period of 30 minutes at ambient temperature of 50 C. Blue line indicates the temperature of Aluminium block and the orange line indicates the temperature variation of the heat pipes. The temperature of the heat pipes rises rapidly at first but gradually falls down to around 52 C which is near to the operating temperature range editor@iaeme.com

8 S. Mahendran, V. Paulson, Stanley Samlal and Pratik Narangikar Figure 9 Phase 2: Copper-Ethanol heat pipes During phase 2A, the setup contains Copper and Ethanol heat pipes and shows satisfactory operation at ambient temperatureof 25 C. During phase 2B, the temperature varies around 53 C which is very near to the operating limit temperature. Figure 10 Graph for Phase 2A: Copper-Ethanol heat pipes Above graph shows the temperature variation of the aluminium block with the Copper- Ethanol heat pipes over a period of 30 minutes at ambient temperature of 25 C. Blue line indicates the temperature of Aluminium block and the orange line indicates the temperature variation of the heat pipes. The temperature of the heat pipes attains a maximum value of 33 C which is well below the operating temperature range editor@iaeme.com

9 Micro Heat Pipe System for Space Avionics Figure 11 Graph for Phase 2B: Copper-Ethanol heat pipes Above graph shows the temperature variation of the aluminium block with the Copper- Ethanol heat pipes over a period of 30 minutes at ambient temperature of 50 C. Blue line indicates the temperature of Aluminium block and the orange line indicates the temperature variation of the heat pipes. Thetemperature of the heat pipes rises rapidly at first but gradually falls down to around 53.1 C which is near to the operating temperature range. Figure 12 Phase 3: Stainless Steel-Acetone heat pipes During phase 3A, the setup contains Stainless Steel and Acetone heat pipes and shows satisfactory operation at ambient temperature of 25 C. During phase 3B, the temperature reduces to around 53 C which is very near to the operating limit temperature editor@iaeme.com

10 S. Mahendran, V. Paulson, Stanley Samlal and Pratik Narangikar Figure 13 Phase 3A: Stainless Steel-Acetone heat pipes Above graph shows the temperature variation of the aluminium block with the Stainless Steel-Acetone heat pipes over a period of 30 minutes at ambient temperature of 25 C. Blue line indicates the temperature of Aluminium block and the orange line indicates the temperature variation of the heat pipes.the temperature of the heat pipes attains a maximum value of 28.7 C which is well below the operating temperature range. Figure 14 Graph for Phase 3B: Stainless Steel-Acetone heat pipes Above graph shows the temperature variation of the aluminium block with the Stainless Steel-Acetone heat pipes over a period of 30 minutes at ambient temperature of 50 C. Blue line indicates the temperature of Aluminium block and the orange line indicates the temperature variation of the heat pipes. The temperature of the heat pipes reduces to51.7 C which is very near to the operating temperature range editor@iaeme.com

11 Micro Heat Pipe System for Space Avionics Figure 15 Phase 4: Performance of system at ambient temperature of -30 C During phase 4, the setup is exposed to an ambient temperature of -30 C for a period of 60 minutes and the temperature of the setup observed over the duration. The setup temperature shows instability withregular variations but manages to keep the temperature well above 0 C. The lowest temperature recorded is 1.1 C. Figure 16 Graph for Phase 4: Performance of system at ambient temperature of -30 C Above graph shows the temperature variation of the aluminium block when it is exposed to an ambient temperature of -30 C. The oscillating pattern is a result of the switching operation. 5. CONCLUSION From the above results, it can be concluded that the designed system acts a local temperature control system and provides successful operation at an ambient temperature within the operating range. For ambient temperature near the operating limits, the system manages to reduce the temperature to values near the operating limits. This system can be coupled with fluid loops to enhance the heat absorption capacity and thus provide better and quicker temperature control editor@iaeme.com

12 REFERENCES S. Mahendran, V. Paulson, Stanley Samlal and Pratik Narangikar [1] Micro-Heat-Sinks for Space Applications, Marco Marengo, S. Zhdanov, L. Chignoli, G. E. Cossali, ASME nd International Conference on Microchannels and Minichannels, ResearchGate, January 2004, 1 5, [2] Thermal Performance of parallel miniature heat pipe system, C.M. Feroz, Mamunur Rahman, Md. HasibulAlam, Auvi Biswas, International conference on Mechanical Engineering (ICME), December 2009, 1 5, [3] Heat Pipes : Review, Opportunities and Challenges, Amir Faghri, Frontiers in Heat Pipes (2014), Global Digital Central, 1 48, [4] Working fluid inventory in miniature heat pipe, T. N. Sreenivasa, S.N. Sridhara, G. Pundarika,, Proceedings of the International Conference on Mechanical Engineering (ICME) December 2005 [5] Advance Cooling Techniques; [6] Micro Heat pipes, Lecture No. # 11, Prof. S. Dasgupta, Dept. of Chemical Engineering, Indian Institute of Technology, Kharagpur [7] Current and Future technologies for Spacecraft Thermal Control 1. Design drivers and current Technologies, M. N. De Parolis& W. Pinter-Krainer, Thermal Control and Rejection Section, ESTEC, Noordwijk, The Netherlands, 9/9/2016; [8] Heat Pipe for Aerospace Applications-An Overview, K. N. Shukla, Journal of Electronics Cooling and Thermal Control, 2015, 5, 1-14; Published Online March 2015 in SciRes. [9] Thermal management of high power multiplexer for a space payload: Contoured micro heat pipe as a viable solution; Darshan Chauhan, V J Lakhera, Rahul Dev, A R Srinivas and D Subramanyam; International Journal of Conceptions on Mechanical and Civil Engineering Vol. 1, Issue. 1, Dec 2013; ISSN: [10] S Girish, K Lavanya and P Geeta Krishna, CFD Analysis of Pulsating Heat Pipe Using Different Fluids, international journal of mechanical engineering and technology, Volume 8, Issue 6, June 2017, pp editor@iaeme.com