RESEARCH ON TRANSIENT REGIME OF A PARAFFIN ACTUATOR

Transcription

1 BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI Publicat de Universitatea Tehnică Gheorghe Asachi din Iaşi Tomul LIX (LXIII), Fasc. 1, 213 SecŃia AUTOMATICĂ şi CALCULATOARE RESEARCH ON TRANSIENT REGIME OF A PARAFFIN ACTUATOR BY ILIE NIłAN* Ştefan cel Mare University of Suceava, Faculty of Electrical Engineering and Computer Science Received: February 2, 213 Accepted for publication: March 22, 213 Abstract. This paper presents a study on an electromechanical actuator with paraffin and Bourdon tube used in positioning applications from the electrical industry. Are shown experimental results obtained for two models of heating sources used to activate the actuator. These experiments led to the drawing of adequate and specificity characteristics which was intended for establishing actuator behavior analysis. Key words: electromechanical actuator, paraffin, Bourdon tube, Peltier element. 2 Mathematics Subject Classification: 74A4, 82D4. 1. Introduction Nowadays, in the field of the mechanical drives were developed different types of devices based, in operation, on the techniques conversion of the various energy sources. Modern technology of achieving actuators is used in a large number of different types of devices and methods for performing mechanical drives. * Corresponding author; nitan@eed.usv.ro

2 22 Ilie NiŃan An actuator can be defined as a device through which energy obtained on the basis of effects and physical principles is converted into mechanical energy, required to drive in rotating or translation motion of some mechanisms. Another definition is that actuator is a device that converts electrical energy or heat energy in a controlled movement. In generally, the structure and operation of most types of actuators is based on one or more techniques drive, such as: electromagnetic drive; magnetostrictive drive; hydraulic drive; pneumatic drive; operation electrothermal; operation electrochemical etc. The electromechanical actuator tested and analyzed in this paper shows the following features: uses low actuation voltages and low actuation currents, shows a small size and small responding time, generates the high driving force, has high storage capacity of energy and a wide range of operating temperature; allows miniaturization, is effective and affordable if you want to be mass production. Broadly speaking, applications from which obtain mechanical work is based on the shape memory effect which it is quantify by the actuators, sensors, etc. Actuators depending on how the supplied energy is converted into mechanical work are divided in thermal actuators and electric actuators. Thus, thermal shape memory actuators, converts thermal energy into mechanical energy, and can be used either to detect a predetermined temperature or for performing mechanical work (Bujoreanu, 22) when it reaches a certain temperature. Therefore, the heat energy is transmitted by conduction, radiation or convection to the shape memory element for to activate actuators. Paraffin actuators are the main opponents of the shape memory actuators. Paraffin actuators general purposes are small containers with a mobile piston. When heated, the paraffin melts, the process is accompanied by a volume increase that moves the piston. At cooling is carried the reverse processing with a thermal hysteresis of 2-5ºC, however, is required the presence of a restoring spring for restoring the plunger to its original position (Schneider & Javor, 1997). Depending on the paraffin type and her composition, the movement of piston may be disproportionate or proportional to temperature; in the latter case, this proportionality is represented by a thermal range that can be reduced (about 15ºC) or wide (approx. 15ºC). In Fig. 1 is illustrated movement-temperature curve of an actuator, in relation to a reduced heat period. Thermal operating range of paraffin actuators is 4-18ºC, the maximum stroke is about 25 mm and force developed is 3 N. My successful applications of paraffin actuators are car thermostats from cooling system with water or oil and valves of heating systems.

3 Bul. Inst. Polit. Iaşi, t. LIX (LXIII), f. 1, Displacement A Displacement A Temperature [ºC] a Temperature [ºC] b Fig. 1 Movement-temperature curve of the main types of thermal actuators, with active stroke (control) denoted by A: paraffin actuator (a); shape memory alloy actuator Cu-(15-25) Zn-(6-8) Al (%)(b) (Carlen & Mastrangelo, 1999). Paraffins (C n H 2n +2 ) as the phase change materials, in the solid state, are characterized by a low thermal conductivity. Yet using additives such as, for example, graphite it can increase the thermal conductivity. Paraffins have a high temperature at melting based according to specific weight, there are noncorrosive, inert and chemically stable below 5 C. At melting, paraffins are characterized by changes in volume and determine the vapor pressure. Making of combination between various different molecular-weight paraffins can easily vary the melting point. Because they are commercially available, the cost of paraffin s is reasonable. One of the reasons that paraffin is used as material for actuators is its volumetric increase at melting (-2%). The paraffin can be loaded to hundreds of MPa and everything presents useful expansion. Paraffin wax has a melting enormous volume expansion because it is actually a solid crystal its shape, with the molecules arranged near. Thus, research on paraffin actuators has been targeted in many directions. A well-defined direction refers to the development of mixtures with thermal expansion: paraffin and graphite (Zhang & Fang, 26); paraffin, silicone rubber and alloys with temperature melting up to 4 F (Pirkle, 1976); paraffin and ferrofluid (Bau & Thompson, 26; Priebe, 1995); paraffin and copper (Haider & Kuder, 1998); paraffin copper and tetrachlorobenzene (Vernet, 1961). Another direction, equally important, is the type of container where paraffin is introduced: cylindrical form of container; bellows form (flexible room) (Huebscher & Sobecks, 1976). A third research direction is the type of heating source used for the paraffin phase change: Peltier element, resistive heating element, heat pump Freon, etc. (Mallet & Kornmann, 1997; Sturdevant et al., 1998). Achievements and worldwide research in paraffin actuators are

4 24 Ilie NiŃan numerous. We recall here the paraffin actuators made by the Centre for Research on machinery and electric drive (EMAD) of the University Ştefan cel Mare Suceava, intended for applications in solar energy (Cernomazu et al., 211a, Cernomazu et al., 211b, Cernomazu et al., 212). 2. The Experimental Test Bench Experimental study includes analysis of two models of electromechanical actuators with paraffin differentiated through the heating source used to change the phase of the paraffin. The attempts of the two types of electromechanical actuators are necessary to establish their behavior in different operating conditions by making adequate and specific characteristics Actuator with Paraffin First Model In the first variant, electromechanical actuator consists mainly of a Bourdon tube made of brass and filled with paraffin (Fig. 2). The Bourdon tube communicates through a pipe with a spherical metal container also filled with paraffin. The entire assembly is secured, through an insulating support, on a support base. The Bourdon tube, the pipe and spherical container are heated through a Peltier element disposed at the bottom of the spherical metal container. Under the action of heat produced by the Peltier element, the paraffin stored inside of the Bourdon tube, passes in liquid state causing through the expansion, changing position of the acted element (Jeder, 212). Fig. 2 Paraffin actuator model I, excited with Peltier element: 1 Bourdon tube; 2 displacement measuring instrument; 3 spherical metal container; 4 Peltier element; 5 DC source. In Fig. 3 are presented the temperature variations of Bourdon tube and for the spherical metal container for a heating cycle and a cooling cycle when the actuator is excited with Peltier element.

5 Bul. Inst. Polit. Iaşi, t. LIX (LXIII), f. 1, Temperature ( C) Electromechanical actuator, first prototype - heating cycle with Peltier element - Spherical container temperature Bourdon tube temperature Temperature ( C) a b ) ) Fig. 3 Bourdon tube and spherical container temperature variation for the first version of the electromechanical actuator: heating cycle (a) and cooling cycle (b) Actuator with Paraffin Second Model In the second variant, paraffin actuator consists of the same basic elements (Bourdon tube, spherical container) except heat source (Peltier element) which was replaced with a heating source by Joule effect, by using a resistor, respectively. In Fig. 4 (Mallet & Kornmann, 1997) are presented test bench for experimental determination of the dynamic characteristics of the paraffin actuator, thermally excited with resistive element. Temperature ( C) Electromechanical actuator, first prototype - cooling cycle, with Peltier element - Spherical container temperature Bourdon tube temperature Temperature ( C) Fig. 4 Paraffin actuator model II, excited with resistive element: resistive: 1 a Bourdon tube; 2 displacement measuring instrument; 3 spherical metal container; 4 resistive element; 5 DC source. In Fig. 5 are presented the temperature variations of Bourdon tube and for the spherical metal container for a heating cycle and a cooling cycle when the actuator is excited with resistive element. The return of the actuator to its initial position for to a new drive cycle is achieved in the first version by polarity reversal of the Peltier element and in the second variant through a fan disposed at the top of the spherical container.

6 26 Ilie NiŃan Temperature ( C) Electromechanical actuator, second prototype - heating cycle with resistor - Spherical container temperature Bourdon tube temperature a Temperature ( C) Temperature ( C) Electromechanical actuator, second prototype - cooling cycle with resistor - Spherical container temperature Bourdon tube temperature b Temperature ( C) Fig. 5 Bourdon tube and spherical container temperature variation for the second version of the actuator with paraffin: heating cycle (a) and cooling cycle (b). The movement variation for the two types of paraffin actuators tested well as time in which this is may be carried out are shown in Figs. 6 a and 6 b, respectively. Actuator displacement x (mm) Electromechanical actuator, first prototype - heating cycle with Peltier element Actuator displacement x (mm) Actuator displacement x (mm) Electromechanical actuator, second model - heating cycle with resistor Actuator displacement x (mm) a b Fig. 6 Movement curve of paraffin actuator excited with: a Peltier element; b resistive element. To verify the results recorded when heating of the actuator was made with resistive element were taken a series of thermal maps (Fig. 7) using an infrared camera, type EaSIR-4. The experimental features presented in Fig. 3 and in Fig. 5, which reflects the transmission of thermal field in Bourdon tube and spherical container, were drawn based on thermal images obtained with the thermal imager.

7 Bul. Inst. Polit. Iaşi, t. LIX (LXIII), f. 1, Fig. 7 Recorded thermal image during operation of the electromechanical actuator (second prototype), taken with a thermal imager, type EaSIR-4. Achieving a thermal analysis is necessary because of the need to optimize the operation and construction of electromechanical actuator, by choosing an adequate heat source or by creating an appropriate thermal expandable mixture, in relation to the assumptions, initially set, relating to application demands in which actuator can operate at a time. By using the thermal image we can determine the time variation of the paraffin temperature profile from spherical container to the end of Bourdon tube. The final conclusions can lead to achieving a thermal expansion mixture with superior properties as regards the operating time respectively the analyzed electromechanical actuator displacement. 3. Conclusions Electromechanical actuators have several advantages that can be generalized: energy saving, saving space and saving resources, minimum investment cost, quick response and modular construction for the development of such systems. The conclusions resulted from experimental analysis refers to proposed electromechanical actuator displacement and its response time which proved to be depending on the thermally expandable mix used and the adopted heat source type. The actuator paraffin movement, made in the first variant, is less than that obtained for the second variant, so it is recommended to use a resistive element actuator for thermal excitation of the actuator. Also, the heating and the cooling of paraffin actuator made in the first version, is carried out with power consumption greater than at the actuator achieved in the second version. The experimental results can lead to achieving a thermal expansion mixture with superior properties as regards the operating time respectively the analyzed electromechanical actuator displacement.

8 28 Ilie NiŃan REFERENCES Bau H., Thompson J., Application of Ferrofluid as a Valve/Pump for Polycarbonate Microfluidic Devices. NSF Summer Undergraduate Fellowship in Sensor Technologies 26 Helen Schwerdt (Biomedical Engineering) - Johns Hopkins University. Bujoreanu L.G., Materiale inteligente. Ed. Junimea, Iaşi, 22. Carlen E.T., Mastrangelo C.H., Simple, High Actuation Power, Thermally Activated Paraffin Microactuator. In: Transducers 99 Conference, Sendai, Japan, June 7-, Cernomazu D., Graur A., Mandici L., Sorea N., NiŃan I., Prodan C., Milici L., Milici M., RaŃă M., Romaniuc I., Actuator cu parafină. Cerere de brevet de invenńie Nr. A/65/211a. Cernomazu D., Mandici L., Graur A., N. Sorea, I. NiŃan, M. RaŃă, L. Milici, M. Milici, C. Prodan, I. Romaniuc, I. Baciu, Actuator solar. Cerere de brevet de invenńie Nr. A/1168/211b. Cernomazu D., Mandici L., Graur A., Sorea N., NiŃan I., RaŃă M., Milici L., Milici M., Prodan C., Romaniuc I., Baciu I., Actuator Solar. Cerere de brevet de invenńie Nr. A/32/212. Haider M.I., Kuder J.E., Thermally Expandable, Viscosity Modified Wax Compositions and Method of use in Actuators. Int. Cl. 6 B29C 35/2. Patent No US /1998. Huebscher R.G., Sobecks R.R., Electro-Thermal Linear Actuator with Internal Reservoir. Int. Cl. 2 F3G 7/6. Patent No US /1976. Jeder (Gugoaşă) M., ContribuŃii teoretice şi experimentale privind noi realizări în domeniul actuatorelor electromecanice cu parafină. Teză de doctorat, Suceava, 212. Mallet O., Kornmann M., Design, Development and Testing of a Paraffin Actuator- Final Report. In: Materials development, design and devices, September, Pirkle F.L., Thermally Expansible Compositions Methods for Preparation and Devices Using Same. Int. Cl. 6 G5D 23/2. Patent No. US /1976. Priebe J., The Utilization of High Output Paraffin Actuators in Aerospace Applications. STARSYS Research Corporation. American Institute of Aeronautics and Astronautics, Schneider E., Javor K.A., Proportionally Controlled Thermochemical Mechanical Actuator. Int. Cl. 6 F3G 7/6. Patent No US /1997. Sturdevant M.L., Allen G.M., Schneider E.T., Thermochemical/Mechanical Brake and Clutch Unit. Int.Cl. 6 : F3G 7/6. Patent, No US /1998. Vernet V., Multi-Range Expansion Material. Patent NoUS3141/1961. Zhang Z., Fang X., Study on Paraffin/Expanded Graphite Composite Phase Change Thermal Energy Storage Material. In: Energy Conversion and Management, 47, 3, February 26, 33 3.

9 Bul. Inst. Polit. Iaşi, t. LIX (LXIII), f. 1, ELEMENT DE EXECUłIE PE BAZĂ DE PARAFINĂ PENTRU APLICAłII DE POZIłIONARE (Rezumat) Lucrarea prezintă studiul unui actuator pe bază de parafină utilizat în cadrul unor aplicańii de pozińionare din industria electrotehnică. Sunt evidenńiate rezultatele experimentale care au avut ca scop stabilirea comportării actuatorului analizat, realizat în două variante constructive, în diferite condińii de funcńionare, prin trasarea unor caracteristici adecvate şi specifice.