Available online at www.sciencedirect.com
ScienceDirect Procedia Engineering 129 (2015) 542 – 548
International Conference on Industrial Engineering
Substantiation of parameters and operation modes of device for thermal comfort of a mobile machine operator Glemba K.V.a,b,*, Averianov Y.I.a,b a
South Ural State University, 76, Lenin Avenue, Chelyabinsk, 454080, Russian Federation b South Ural state agrarian University, Chelyabinsk 454080, Russia
Abstract The effects of heat and cold on the human body lead to a reduction in its protective power and reserve capacity. The productivity of operators is reduced by 25~55% with ambient temperature increasing up to 28~31°C. It is proved that the temperature and human performance have a strong correlation. The process of forming the thermal state of the human operators in the cabs of mobile machines is still to be understood by automotive engineers. On the basis of theoretical research, we have identified the main factors influencing the thermal state of the human body, justified the blueprint and design parameters of the proposed device for thermal regulation. There is a power dependence of heat flux on the thickness of the operator’s clothes, the power, and distance of their body from the local device. When experimenting with the relationships between the human operator’s thermal state (thermal sensation) indicator and the parameters of microclimate in the mobile machine cabs, we considered the operating modes of the device. Experimental studies were carried out in a climatic chamber based on a unified cabin. The experiments determined the value of the power density of the heat flow. It amounted to 486 watts; this will be needed in the future to calculate the constructive and regime parameters of the proposed device. © 2015 2015The TheAuthors. Authors. Published Elsevier © Published by by Elsevier Ltd.Ltd. This is an open access article under the CC BY-NC-ND license Peer-review under responsibility of the organizing committee of the International Conference on Industrial Engineering (ICIE(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the International Conference on Industrial Engineering (ICIE-2015) 2015). Keywords: The operator of the mobile machine; thermal comfort; conductance; thermoregulation; thermal sensation; the climate; the heat flux.
* Corresponding author. Tel.: +7-351-262-1347. E-mail address:
[email protected]
1877-7058 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the International Conference on Industrial Engineering (ICIE-2015)
doi:10.1016/j.proeng.2015.12.055
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1. Introduction The level of conditions and safety in the workplace operators of automotive engineering determines its demand and the competitiveness of the market. High power equipment and complexity of control systems in modern mobile machines (MM) requires a search for new solutions to create comfortable conditions for the work of the human operator. The causes and the degree of reduction human performance are defined by the thermal condition of his body and its heat content. Scientists say that high efficiency is maintained for 6 hours at the heat content in the body 128 kJ/kg and decreases over time by 10~20%. But if you increase the value to the level of 129~131 kJ/kg return is reduced at the same time by 30~45%. In a cold climate an increase in the mass of clothes is the cause of poor performance. For example, the energy consumption of the body increases by 18% when performing the same job by increasing the mass of clothing from 4.3 to 6.5 kg. The effects of heat on the human body in conditions of heating microclimate leads to a reduction in its protective power and reserve capacity. The cold also affects the cardiovascular system and blood pressure. Observed dystonia and exacerbated chronic disease. The productivity of the human operator is reduced by 25~55% with increasing ambient temperature until the interval of 28~31°C, and reducing the skills of workers leads to a more intense decrease in performance [1 – 6]. 2. Methods 2.1 Theoretical research The influence of microclimate on the health of operators in the cabs MM devoted a significant amount of research. Human thermal comfort is one of the main factors that characterize the conditions of the production environment, the health and well-being, the degree of job satisfaction. It is proved that there is a high level of correlation between the temperature regime and the level of human activity. It was found that people performing work of moderate severity with the energy consumption of 313 watts (40 minutes work, 20 minutes rest) under conditions of heating microclimate occurs a pronounced decrease of efficiency, especially under thermal impact. Solution of tasks to ensure the comfortable state of the human operator in the cabins MM is a rather complex problem. The device of an artificial microclimate must meet the requirements of simplicity of design, low cost of fabrication, possibility of service personnel of low qualification, they must ensure that the design conditions with constantly changing modes of operation of the machines. Partial reduction of the air temperature in the cabin at the expense of natural ventilation leads to an increase in speed of air movement and dust accumulation in it. Currently numerous experimental studies have established a negative influence of adverse environmental conditions on productivity [7 – 25]. Many papers are devoted to the study of the formation of the thermal state of the human organism in the conditions of industrial premises. However, the process of forming the thermal state of the human operator in spaces of small closed volume, such as the cockpit MM remains poorly understood. This makes it difficult not only to control the thermal state (thermal comfort) of a person in the cockpit MM and evaluation of the effectiveness of normalization of the microclimate in their selection, testing and use, this hampers the development of new ways and means to ensure a comfortable state of the human operator [5, 6]. For the last time on the basis of the principles of control theory created a number of models of temperature regulation of man. In these models, represented the human body in the form of geometric segments, each subdivided into a number of layers and compartments. Passive thermoregulation system can be described using the heat balance equation for each compartment, taking into account the contact surface of the skin with the environment. On the basis of established reference temperature for each compartment in the system are formed by control signals, allowing you to modify physiological responses during exposure to various environmental factors, physical load and thermal resistance. Scientists recognized system Stolwijk J. A. J. in the field of thermoregulation, designed to study the thermoregulatory responses of the body in the field of positive temperatures. This model was the most appropriate for the interval of temperatures from 25~48°C and has a complex system of generation of control signals and their distribution, taking into account the deviation of the temperature values of each compartment and the reference level. The researchers obtained important information when using mathematical modeling to describe the thermal regime of the body. So, Gagge A. R. and co-authors have developed an index of effective temperature, which has been used in the practice of evaluation of physiological strain of an organism when exposed to a thermal
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factor of the environment, using compartmental models. In the process of analysis of mathematical models describing the formation process of the thermal state of the human body, found that some authors do not take into account or neglected component of thermal balance – thermal conduction. Conducted targeted impact on certain portions of the surface of the human body will facilitate the process of heat exchange of the organism with the external environment under certain conditions, heating or cooling climate. To date remains unresolved question about the levels and modes of the thermal effects on the human body where there is no overstrain of thermoregulatory mechanisms of the body, where there is no local thermal discomfort. Conductive heat exchange of the human body contacting surfaces and means of ensuring thermal comfort of the human body deserves serious study [1 – 6, 12 – 14, 23 – 25]. 2.2. Research methods The methodology of the experimental studies included the measurement of microclimatic conditions in the external environment and in the interior of MM, a survey of the human operator on its thermal state, i.e. about the thermal sensation. In addition, the recorded date, time, and place of the research, the type of work performed, age and clothing of operator, weather conditions (cloud cover and solar radiat). Objectives of the experimental studies was to obtain experimental dependencies between the indicator of the thermal state (thermal sensation) of the human operator and the parameters of the microclimate in the cabins MM, the justification of the thermal state of the body (heat content and thermal sensation) of the human operator based on the parameters and operating modes of local thermally regulating devices (LTRD) in the cockpit MM. Field studies were conducted in weather conditions of the transition period, the regions of the southern Urals and Northern Kazakhstan. The outdoor temperature varied in the range of 10~31°C, relative humidity – 20~80%; standard deviation-wind speed – 0.5 to 6.0 m/s, cloudy – one or two points. Measurement of microclimate parameters in the cabins was carried out at performance of technological processes when you load the engines by 70% (r15%) from the nominal value. For research were selected groups of people from 5 to 10 people in the age 20~40 years old, not adapted to the specific working conditions of the operator MM. Performed work of moderate severity, the clothes were summer with a thermal resistance of 0.5~0.6 clɨ (1 clo = 0,155 (m2 K)/W), the subjects familiarized with the modified scale of scores of thermal sensation, characterizing the thermal state of the operator. The studies were conducted during the working time. We measured microclimate parameters at the time of the evaluation in humans of one of established his thermal sensations in the cockpit MM. Measurements of microclimate parameters in the cockpit MM was carried out at three points: at the feet, at chest level and in the breathing zone. Repeated measurements were 25 times [3~6]. 2.3. Experimental studies As optimization criteria have been selected heat content and thermal sensation of the human operator. They reflect a comfortable thermal state of the body and can be evaluated by the criteria of comprehensive assessment of comfort conditions of microclimate. On the basis of theoretical research identified the main factors influencing the process of formation of the thermal state of the human body. Below is the diagram of the LTRD (Fig.1) and parameters of its design – the diameter and pitch of the tubes (Fig.2). Criteria for evaluation of the thermal state of the human operator are its qh heat content and thermal sensation Sh. They are characterized by the parameters of the microclimate in the cockpit MM, are based on the characteristics and operating modes of the LTRD. For the purpose of characteristics of the comfort areas it is proposed to introduce the concept of criteria of comfort, a numeric value which can be determined from the following expressions in Eq. (1) and Eq. (2) [1, 2]. kkS
kS ( Sha Shn ) Shn ,
(1)
kkq
kq (qha qhn ) qhn ,
(2)
where kks, kkq is the criteria comfort of microclimate due to the evaluation of thermal sensation and thermal content of man, conditional units; kS, kq is the normalizing coefficients of thermal sensation and thermal content of human
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rights, taking into account the conversion into conventional units; Sha, Shn is the actual and normative values of thermal sensations, score; qha, qhn is the actual and normative values of specific heat content, (kJ/kg).
Fig. 1. Scheme of the experimental sample local thermally regulating devices, 1 removable cover, 2 airbag, 3 back, 4 and 5 respectively the collector inlet and outlet, 6 pump, 7 a liquid flow regulator, 8 accumulator, 9 and 10 flexible tubing, from 11 to 14 respectively, of the tube outlet and inlet of the thermal unit and cooling unit.
Fig. 2. The experimental sample of the device for the thermal comfort of the local action.
Experimental studies were carried out in a climatic chamber, which was established on the basis of a unified cockpit MM [3-6]. Parameters of microclimate in a climatic chamber maintained at a predetermined level when the doors and Windows closed during the whole time of the experiment, the indicators were: air temperature 32 ±0.5ºC, relative humidity of 40~60% and air speed of 0.2~0.4 m/s. Periodically changed work LTRD by the method of experiment planning. The flow rate of fluid when the work has not changed and amounted to 120 liters/hour.
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3. Results Effective operation of the device according to the criterion of comfort with regard to reflecting thermal sensation depends on the subjective perception of the environment. There is a dependence of the power thermal flux from such quantities as the gap between the body of the human operator and LTRD, thickness of clothing of the operator, etc. It is therefore necessary experimental validation of microclimate parameters with minimum absolute values of the criteria categories, such as modes of operation is the temperature of the liquid (tl, °C), and the design of the components is the total length of the tubes LTRD (L, m). The authors have built a graphic dependence (Fig.3), which links the parameters with the required power of the heat flux, fluid temperature, flow rate, etc. Thus, if the change in temperature of the fluid be in the range of 16~24°C, then the required total length of tubes will be in the range of 18~23 m. Of greatest interest is the dependence of the power density of the heat flow from the speed of increasing the temperature of the human body (Fig. 4), since this speed determines the degree of comfort to the proposed LTRD. The power density of the heat flux significantly increases with increasing speed of increasing temperature of the human body and is 150 W/m2 per 1°C. This is independent from the mass or growth. The required average power density of the heat flow is 268 W/m2 at mean values of body mass and human growth (70 kg and 1.7 m) and the normative value of the speed of increase of body temperature (2°C per hour).
Fig. 3. Graphic dependence of the required total length of the tubes L [m] from the temperature of the liquid tl [°C] according to the condition of minimality criteria of comfort, 1 the heat content of the body, 2 thermal sensation, 3 integral criterion.
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Fig. 4. The dependence of the power density of the heat flow qT [W/m2] from the rate of rise of body temperature ǻtT/ǻIJ [°C/h] for an average growth of Hh=1.75 m, at its mass mh [kg].
The values of power density of the heat flow is easy to determine the full power of the heat flux on the entire surface of the human body, essential for maintenance of a desired (comfortable) speed temperature rise by multiplying the power density of the heat flux on the surface area of the human body. In this regard, graphical dependencies for full power heat flux are not shown. However, the value of the total power of the heat flux with standard parameter values were calculated and amounted to 486 watts. This value of power density of heat flow is necessary for further calculations of the design and operation of the LTRD. 4. Conclusion Cabin equipment LTRD has the following advantages in comparison with a serial cabin, having a conventional air conditioning system or ventilation. Usage in the cabins LTRD is effective to reduce the excess heat content of the human operator. The use of liquid as the coolant provides maximum heat transfer from the surface of the human body (the heat transfer coefficient from the human body to the liquid is greater than air, the energy costs for the circulation of liquid is smaller than for air circulation). The improvement of working conditions through the use of a LTRD involves increasing production per unit of working time without excessive tension of functional systems of the human body. Is the time savings due to the reduction of losses due to temporary disability. Creates an increase in the volume of manufactured goods by reducing non-productive expenditure of energy to overcome the adverse conditions of a human operator. It was established experimentally the relationship between comfort, climate and heat sensation and heat content of the body of the human operator. Becomes possible to make the best assessment of efficiency of functioning of the device, correcting the thermal state of the human operator. Developed experimental design sample the LTRD to ensure a comfortable thermal state of the human operator in the cockpit MM. The experimentally determined value of the power density of the heat flow required for optimum calculations, both constructive and regime parameters of the LTRD. References [1] K.V. Glemba, Yu.I. Averyanov, V.N. Kozhanov, An integral criterion for the evaluation of comfort conditions of microclimate in the cabins of mobile agricultural machines, Tractors and agricultural machinery. 4 (2005) 36–38. [2] K.V. Glemba, Yu.G. Gorshkov, Yu.I. Averyanov, I.N. Starunova, Indicators of working conditions and fatigue of operators of mobile agricultural machines, The journal Science, Kostanay. 2 (2003) 11–17. [3] K.V. Glemba, Improving working conditions and reducing injuries operators of mobile wheel cars of agricultural purpose: Cand. Sci. (Eng.) Dissertation, Chelyabinsk, 2004. [4] K.V. Glemba, Improving working conditions and reducing injuries operators of mobile wheel cars of agricultural purpose: abstract Cand. Sci. (Eng.) Dissertation, Orel, 2004. [5] Yu.I. Averyanov, The improvement of working conditions of operators of mobile agricultural machinery the application of local heat regulating device: Cand. Sci. (Eng.) Dissertation, Chelyabinsk, 2000.
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K.V. Glemba and Y.I. Averianov / Procedia Engineering 129 (2015) 542 – 548 [6] Yu.I. Averyanov, Improving the safety of the process of harvesting grain crops on the basis of improving the system operator – machine – environment: Dr. Sci. (Eng.) Dissertation, Chelyabinsk, 2006. [7] K.V. Glemba, Yu.G. Gorshkov, Yu.I. Averyanov, I.N. Starunova, S.Yu. Popova, The hazards of mobile technological processes, Mechanization and electrification of agriculture. 7 (2003) 4–6. [8] K.V. Glemba, Yu.G. Gorshkov, Yu.I. Averyanov, O.F. Skornyakov, I.N. Starunova, Evaluation of potential process safety subsystems, Tractors and agricultural machinery. 12 (2003) 40–41. [9] K.V. Glemba, O.N. Larin, Yu.I. Averyanov, Aspects of increasing the security subsystem operator in transport on wheels, Agro-industrial complex of Russia. 70 (2014) 34–42. [10] K.V. Glemba, Yu.I. Averyanov, The results of the research of functional parameters of training of operators of mobile machines, Proceedings of the conference Chelyabinsk state Agroengineering Academy, Chelyabinsk. (2015) 134–140. [11] K.V. Glemba, O.N. Larin, Review of methods of determining the reliability of the operator in dynamic ergatic systems, Transport in the Urals. 32(1) (2012) 17–22. [12] K.V. Glemba, Yu.I. Averyanov, V.K. Glemba, Methods of evaluation of information overload for the operator in the machine control, Bulletin Chelyabinsk state Agroengineering Academy, Chelyabinsk. 56 (2010) 5–10. [13] K.V. Glemba, Yu.I. Averyanov, Identifying and improving problematic relationships of structural elements of the system safety movement of mobile machines, Bulletin Chelyabinsk state Agroengineering Academy, Chelyabinsk. 66 (2013) 25–34. [14] K.V. Glemba, Yu.G. Gorshkov, Yu.I. Averyanov, O.F. Skornyakov, N.V. Svetlakova, The indicator of the level of skill of the operator of a mobile agricultural machine, Tractors and agricultural machinery. 3 (2005) 32–35. [15] K.V. Glemba, Impact on road safety of pertinence of the information field, Agro-industrial complex of Russia. 68 (2014) 7–13. [16] K.V. Glemba, S.V. Gorbachev, Impact on traffic safety level information flow formalization in ergatic systems, Bulletin of Orenburg state University, Orenburg. 129(10) (2011) 88–93. [17] K.V. Glemba, O.N. Larin, V.I. Mayorov, The application of a systematic approach to improve road safety, Monthly scientific journal Transport: science, technology, management, Moscow. 11 (2013) 52–55. [18] K.V. Glemba, The influence of perceptual processes, spatial perception of road users on safety, Bulletin Chelyabinsk state Agroengineering Academy, Chelyabinsk. 62 (2012) 26–31. [19] K.V. Glemba, Yu.G. Gorshkov, Yu.I. Averyanov, I.N. Starunova, E.V. Shamanova, Security maintenance machines, Mechanization and electrification of agriculture. 11 (2003) 21–22. [20] K.V. Glemba, Yu.G. Gorshkov, Yu.I. Averyanov, I.N. Starunova, S.Yu. Popova, Automatic control of serviceability of brake system, Tractors and agricultural machinery. 5 (2003) 20–22. [21] K.V. Glemba, O.N. Larin, Influence of traffic organization on the process of perception of the driver information, Monthly scientific journal Transport: science, technology, management, Moscow. 11 (2012) 55–57. [22] K.V. Glemba, Yu.G. Gorshkov, Yu.I. Averyanov, E.Yu. Kulpin, I.N. Starunova, Rationale a safe speed wheeled vehicles, Mechanization and electrification of agriculture. 12 (2002) 27–30. [23] V.M. Mishurin, A.N. Romanov, The reliability and safety of the driver, Transport Publishing House, Moscow, 1990. [24] E.V. Gavrilov, Ergonomics in road transport, Publishing House Technika, Kiev, 1976. [25] A.S. Aruin, V.M. Zatsiorskiy, Ergonomic biomechanics, Moscow, 1988.
