CC BY
40
DOI: 10.24143/2073-1574-2017-4-62-71 УДК 621.431.74.068.4:662.76
S. V. Vinogradov, Hoang Trung Huan, Nguyen Cong Doan
DESIGN AND CALCULATION OF A THERMOELECTRIC GENERATOR FOR SHIP POWER PLANTS
Abstract. The article presents the design of a thermoelectric generator (TEG) for utilizing heat energy of exhaust gases of ship diesel engines. There have been chosen a TEG basic design and a technique for its efficiency raising. Geometric, heat and electric parameters of TEG have been calculated using RSD 49 ship project. Calculation of heat and electric parameters of TEG with intensive heat exchange on the surface of a hot node was made using sloping plates. The relation between TEG position (before and after exhaust boiler) and a Wartsila 6L20 main engine exhaust system has been determined. According to the analysis result, in case of TEG position after exhaust boiler and 100% load of main engine, estimates increased compared to a basic design: performance - 4%, capacity - 5%; output gas temperature decreased to 1%. At combined operation of TEGs positioned in the exhaust system of one main engine with exhaust boiler shut down and TEG positioned after exhaust boiler, estimates grew: capacity - 35%, performance - 14%; output gas temperature decreased to 19%. Total maximum capacity of TEGs positioned in the main engine exhaust systems makes 42.78 kW which is 1.78% of a ship power plant capacity.
Key words: thermoelectric generator, RSD 49 project ship, Wartsila 6L20 diesel engine, heat utilization, exhaust gases, intensification of heat exchange.
Introduction
The issue of efficient use of fuel is of current importance for the fleet. It is known that in the main engines of the ship power plant (SPP), up to 50% of the combustion heat of the fuel is converted into mechanical energy. The rest of the energy is lost. Also, one of the solutions to this problem is the use of thermoelectric effect for converting heat energy of exhaust gases (EG) from marine diesel engines into electric ones.
Thanks to the latest advances in the development of thermoelectric materials and systems, interest in the use of the thermoelectric generator TEG in SPP was renewed. Advantages of TEG are a significant resource, lack of moving parts, quiet operation, environmental cleanliness, versatility with regard to the methods of supply and removal of heat and the possibility of recovering the waste heat energy. The disadvantage of TEG is a low efficiency of 1-10%. Despite this, thermoelectric generators have been extensively utilized.
This work is devoted to the issues of increasing the efficiency of TEG due to the intensification of heat transfer. The design of TEG with altered surfaces of the heat exchanger from the side of exhaust gases of the internal combustion engine is proposed, and changes are made in the method for calculating thermal and electrical parameters of TEG, taking into account the features of heat exchange processes with intensified TEG surfaces.
Power plant of RSD 49 project vessel
RSD 49 project vessels, in accordance with the classification adopted by Marine Engineering Bureau, belong to Volga-Don Max class. It means they have maximum displacement and dimensions for the Volga-Don shipping canal. Ships of the series can be used for transportation of general, bulk, timber, grain, bulky and dangerous goods in international traffic. Technical and operational characteristics of the vessel and engines are presented in Table 1.
The propulsion system at "RSD 49 project vessel" consists of 2 Wartsila 6L20 engines, whose output flange is rigidly connected to the shafting and fixed-pitch propeller. The main engine (ME) gas system includes: a pipeline with an inner diameter of 420 mm and an outer diameter of 600 mm, thermal expansion joints, an AELBORG UNEX P-2 steam recovery boiler (SRB).
Table 1
Operating characteristics of RSD 49 project vessel
Characteristics Unit Value or response
Calculated vessel length m 139.95
Width m 16.5
Hull height m 6.0
Draft m 4.70
Deadweight t 7143
Loaded sailing rate knots 11.5
Capacity of main propulsion of SPP kW 2 ■1200
Auxiliary diesel gases kW 2 ■ 292
Power plant type N/A Combustion engine
Type of power delivery to propulsion shaft N/A Mechanic
Since TEG is recommended to be installed vertically, two locations were chosen for its installation, after the engine and after the recovery boiler. As a basic version of TEG, the construction proposed by the authors in [1] was chosen.
Table 2
Operating characteristics of exhaust gas system of Wartsila 6L20 engine
Exhaust gas system
Flow rate at 100% load kg/s 2.57
Flow rate at 85% load kg/s 2.25
Flow rate at 75% load kg/s 1.95
Temperature after turbo charger, 100% load (TE517) °C 305
Temperature after turbo charger, 85% load (TE517) °C 295
Temperature after turbo charger, 75% load (TE517) °C 305
Choosing thermo generator modules
In this installation, thermo generator modules of TrM-287-1.0-1.5 type by KRYOTERM OJSC are used, whose design and electrical characteristics are presented in Tables 3 and 4 [2]. The construction of the thermo generator module is shown in Fig. 1.
Table 3
Design characteristics of TrM-287-1,0-1,5 thermo generator module
Module type Size range Electrical resistance, Rm Heat resistance
Length, mm Width, mm Height, mm Ohm kW
TrM-287-1.0-1.5 40 40 3.8 4.72 1.16
Table 4
Electrical characteristics of TrM-287-1.0-1.5 thermo generator module*
Characteristics tc = 50°С, th = 150°С tc = 100°С, th = 200°С
Voltage, V 4.77 4.52
Current rate, A 0.47 0.43
Capacity, W 2.23 1.93
Power efficiency, % 2.7 2.3
* tc - temperature of cold side; th - temperature of hot side. The parameters are indicated for the load resistance equal to the electrical resistance of the module.
Cold side
P-type semiconductor P
N-type semiconductor
Isolator (ceramic)
Fig. 1. Thermoelectric module
Design and calculation of TEG with heat transfer augmentation on the surface of the hot unit for installation before UB
The calculation procedure is similar to that specified in [3], Fg =
a23V3 2
, with corrections that
take into account the use of inclined plates on the surface of the hot unit. In particular, the calculation of the heat transfer coefficient of gas was changed.
Cross-section area of flue, m :
F = 2
- F
H'
where a - size of the wall face of the hot node, m; FH - cross-sectional area of inclined plates, m Cross-sectional area of inclined planes, m2:
FH = 12hSsin9,
where h - height of the inclined plane, m; S - element thickness, m; 9 - inclination angle. Clearance between inclined planes, m2:
L - SN _
N-p -1
where L - length of the heat exchanger, m; Ni-p - number of inclined planes in TEG. Gas rate, m/s:
G„
=
5. • h (Nt_p -1)
where Gg - gas consumption, kg/s. Heat transfer surface area, m2:
F =
-Q-+F ,
k -At psa
where Fpsa - plate surface area; tag - average gas temperature. Reynolds number for gas
tog • defd
Reg =-,
Vg
where vg - kinematic viscosity of gas, m2/s; defd - equivalent flue diameter, defd =, m.
6a
Exhaust gas of the diesel engine moves in the pipeline in turbulent regime, therefore the Nusselt number for the gas is determined by the formula [4-6]
Nug = 0,008Reg'9 • Pr g0 43,
where Prg - Prandtl number for gas.
Coefficient of convective heat transfer for gas with augmentation of heat transfer on the surface of a hot unit:
Nug • Xg
a
h-c 7 9
defd
where Xg - coefficient of thermal conductivity of gas, W/(m2 • K).
It follows from the calculation results that the convective heat transfer coefficient for gas with augmentation of heat transfer on the surface of a hot unit is 7.3 times greater than convective heat transfer coefficient on a smooth surface of a hot part.
According to the recommendations of the author of work [7], dimensions, slope angle, number and material of the plates were adopted. In accordance with the design of ME exhaust gas system, a TEG was designed with an heat transfer augmentation on the surface of the hot unit installed after the UB (Fig. 2).The calculation is performed for TEG at 75, 85 and 100% for ME loads. The results of calculations of the joint work of ME and TEG are given in Table 5.
Table 5
Results of calculations for one TEG with the heat transfer augmentation on the surface
of the hot unit installed before UB
N, % P, kW I, А U, V Goutput. gi kg/s t output t output
75 5.8 16.72 352 1.95 240.9 38
85 5.75 16.62 346.43 2.25 240.5 38
100 6.09 16.92 360.12 2.57 255.3 38
и
0110 0-------------О 0100 т
678
Fig. 2. TEG design with heat transfer augmentation, established before UB
Design and calculation of TEG with heat transfer augmentation for installation after UB
^ a 23л/э
Calculation procedure is similar to that specified in cl. [3], Fg = —^— as amended in "Design
and calculation of TEG with heat transfer augmentation on the surface of the hot unit for installation before UB". In accordance with Fig. 3, TEG design with heat transfer augmentation on the surface of the hot unit, installed after UB has been developed (Fig. 3).
Fig. 3. TEG design with heat transfer augmentation, established after UB
The results of the calculation of TEG with heat transfer augmentation established after UB are presented in Table 6.
Table 6
Results of calculations for one TEG with the heat transfer augmentation on the surface of the hot
unit installed after UB
N, % P, kW I, А U, V Goutput. gi kg/s t^output t output ОС
100 9.7 45 216 2.57 98 26
Calculation of TEG collaboration indicators, when UB is off
Calculation results of TEG collaboration indicators are presented in Table 7.
Table 7
The results of calculations of TEG installed into the systems of gas hammer of one ME in joint operation with an idle UB
TEG Ne, % P, kW I, А U, V GOutput. g? kg/s t^output ОС f output lw 1 С
Before UB 100 6.09 16.92 360.12 2.57 255.3 38
After UB 100 15.3 56.6 270.4 2.57 122 28
Analysis of calculation results
Based on the results of calculations, it can be concluded that the use of a heat transfer surface with inclined surfaces makes it possible to increase the efficiency of TEG operation.
When TEG was installed before UB, the calculated values were increased in comparison with the basic design, in accordance with Fig. 4 and 5 - efficiency by 4%, power by 6%, and exhaust gas temperature at the outlet from TEG decreased by 1%. Gas rate has increased by 12%, but its value is within the permissible limits, which allows to conclude that the installation of inclined surfaces does not lead to significant aerodynamic resistance of the gas-sluice system.
6.2
55.8
35
.1? 56 %
%
° 54
5.2
75
85
Engine load, %
TEG with modified heat transfer surface
100
TE G of the base version
Fig. 4. Comparison of TEG power of the base version and TEG with modified heat transfer surface
4,15
4,1
4,05
<D
g 395
3,9
3.85
3.8
75 85
Engine load, %
TEG with modified heat transfer surface
100
TEG of the base version
Fig. 5. Comparison of efficiency of TEG base version and TEG with modified surface
When TEG was installed after UB at 100% ME load, calculated values increased: efficiency by 4%, power by 5%, and exhaust gas temperature at the outlet from TEG decreased by 1%, compared to the basic design in accordance with Fig. 6, 7.
ä &
О
10000 9900 9800 9700 9600 9500 9400 9300 9200
TEG with modified heat transfer surface
TEG of the base version
Fig. 6. Comparison of TEG power of the base version and TEG with modified heat exchange surface
0.0338 0.0336 0.0334 0.0332
a
<D
О
Й 0.0328 W
0.0326 0.0324 0.0322
TEG with modified heat tranffer sufface
TEG o tthe base version
Fig. 7. Comparison of efficiency of TEG base version and TEG with modified surface
The results of calculations of the joint operation of TEG, with UB off, in accordance with Fig. 8 and 9, showed an increase in TEG installed after UB: power by 35%, efficiency by 14%, exhaust gas temperature at the outlet from the TEG decreased by 19%.
О
18000 16000 14000 12000 10000
^ 8000
6000 4000 2000 0
TEG installed after UB, joint operation
TEG installed after UB
Fig. 8. Comparison of power of TEG installed after UB and in joint operation
0х
iê 'о £ W
0.04 0.039 0.038 0.037 0.036 0.035 0.034 0.033 0.032 0.031 0.03
TEG installed after UB, joint operafton
TEG installed after UB
Fig. 9. Comparison of efficiency of TEG installed after UB and in joint operation
Conclusion
According to the calculation results obtained, the authors can infer:
- the use of heat exchange surface when using inclined plates allows to increase the efficiency of TEG operation;
- with TEG installed after UB at 100% ME load calculated values increased, compared to the basic design in accordance with Fig. 6, 7: efficiency by 4%, power by 5%, and exhaust gas temperature at the outlet from TEG decreased by 1%;
- the results of calculations of the joint operation of TEG, with UB off, in accordance with Fig. 8 and 9, showed an increase in TEG installed after UB - power by 35%, efficiency by 14%, exhaust gas temperature at the outlet from the TEG decreased by 19%;
- the total maximum power of TEG installed in the systems of ME exhaust gas systems is 42.78 kW, which comprises 1.78% of the power of SPP and 7.32% of the power of combustion engine;
- TEG utilization is advisable for passenger and container vessels;
- to convert DC electric current into alternating current, it is necessary to install an inverter with accumulators to store the TEG in the electrical system of the vessel.
The article presents a new design of TEG with hot surfaces located in inclined panels. Results of calculations are presented in the article showing that when the surface area of a hot section heat exchanger changes, the convective heat transfer coefficient for gas with heat exchange augmentation on the surface of a hot unit is 7.3 times greater than the convective heat transfer coefficient on a smooth surface of a hot part. The authors investigated the influence of inclined plates on the exhaust gas flow; the study results will be presented in the next article.
REFERENCES
1. Rossiiskii morskoi registr sudokhodstva. Registrovaia kniga sudov [Russian Maritime Register of Shipping. Register of ships]. Available at: http://www.rs-class.org/ru/.
2. Available at: http://kryotherm.ru.
3. Vinogradov S. V., Khalykov K. R., Nguen K. D. Metodika rascheta i otsenki parametrov eksperi-mental'nogo termoelektricheskogo generatora [The technique of analysis and assessment of a pilot thermoelectric generator characteristics]. Vestnik Astrakhanskogo gosudarstvennogo tekhnicheskogo universiteta. Seriia: Morskaia tekhnika i tekhnologiia, 2011, no. 1, pp. 84-91.
4. Nashchokin V. V. Tekhnicheskaia termodinamika i teploperedacha [Technical thermodynamics and heat transfer]. Moscow, Vysshaia shkola Publ., 1975. 496 p.
5. Isachenko V. P. i dr. Teploperedacha [Heat transfer]. Moscow, Energiia Publ., 1975. 488 p.
6. Kutateladze S. S. Osnovy teorii teploobmena [Fundamentals of Heat Exchange]. Moscow, Atomizdat, 1979. 416 p.
7. Simulation and experimental study on thermal optimization of the heat exchanger for automotive exhaust-based thermoelectric generators. Case Studies in Thermal Engineering, 2014, no. 4, pp. 85-91.
The article submitted to the editors 19.09.2017
INFORMATION ABOUT THE AUTHORS
Vinogradov Sergey Vladimirovich - Russia, 414056, Astrakhan; Astrakhan State Technical University; Candidate of Technical Sciences, Assistant Professor; Professor of the Department of Operation and Maintenance of Water Transport; [email protected].
Hoang Trung Huan - Russia, 414056, Astrakhan; Astrakhan State Technical University; Master's Course Student of the Department of Operation and Maintenance of Water Transport; [email protected].
Nguyen Cong Doan - Vietnam, Hanoi; University of Transport Technology; Candidate of Technical Sciences; Head of Department of Ship Power Plants; [email protected].
С. В. Виноградов, Хоанг Чунг Хуан, Нгуен Конг Доан
КОНСТРУКЦИЯ И РАСЧЕТ ТЕРМОЭЛЕКТРИЧЕСКОГО ГЕНЕРАТОРА ДЛЯ СУДОВЫХ ЭНЕРГЕТИЧЕСКИХ УСТАНОВОК
Представлена конструкция термоэлектрического генератора (ТЭГ) для утилизации тепловой энергии отработавших газов судовых дизелей. Выбрана базовая конструкция ТЭГ и метод повышения его эффективности. Геометрические, тепловые и электрические па-
раметры основного ТЭГ рассчитаны на примере судов проекта RSD 49. Произведен расчет тепловых и электрических показателей ТЭГ с интенсификацией теплообмена на поверхности горячего узла при применении наклонных пластин. Определено влияние места расположения ТЭГ (до и после утилизационного котла) на газовыхлопную систему главных двигателей Wartsila 6L20. По результатам расчета ТЭГ с интенсификацией теплообмена, установленного после утилизационного котла, в режиме 100 % нагрузки ГД, увеличились расчетные показатели по сравнению с базовой конструкцией: КПД на 4 %, мощность на 5 %, а температура газов на выходе из ТЭГ снизилась на 1 %. При совместной работе ТЭГ, установленных в системы газовыхлопа одного ГД при выключенном утилизационном котле, увеличились расчетные показатели ТЭГ, установленного после утилизационного котла: мощность на 35 %, КПД на 14 %, температура газов на выходе из ТЭГ снизилась на 19 %. Суммарная максимальная мощность ТЭГ, установленных в системах газовыхлопа ГД, - 42,78 кВт, что составляет 1,78 % мощности СЭУ.
Ключевые слова: термоэлектрический генератор, судно проекта RSD 49, дизель Wartsila 6L20, утилизация теплоты, выхлопные газы, интенсификация теплообмена.
СПИСОК ЛИТЕРА ТУРЫ
1. Российский морской регистр судоходства. Регистровая книга судов. URL: http://www.rs-class.org/ru/.
2. URL: http://kryotherm.ru.
3. Виноградов С. В., Халыков К. Р., Нгуен К. Д. Методика расчета и оценки параметров экспериментального термоэлектрического генератора // Вестн. Астрахан. гос. техн. ун-та. Сер.: Морская техника и технология. 2011. № 1. С. 84-91.
4. Нащокин В. В. Техническая термодинамика и теплопередача. М.: Высш. шк., 1975. 496 с.
5. Исаченко В. П. и др. Теплопередача. М.: Энергия, 1975. 488 с.
6. Кутателадзе С. С. Основы теории теплообмена: 5-е изд., перераб. и доп. М.: Атомиздат, 1979. 416 с.
7. Simulation and experimental study on thermal optimization of the heat exchanger for automotive exhaust-based thermoelectric generators // Case Studies in Thermal Engineering. 2014. No. 4. P. 85-91.
Статья поступила в редакцию 19.09.2017
ИНФОРМАЦИЯ ОБ АВТОРАХ
Виноградов Сергей Владимирович — Россия, 414056, Астрахань; Астраханский государственный технический университет; канд. техн. наук, доцент; профессор кафедры эксплуатации водного транспорта; [email protected].
Хоанг Чунг Хуан — Россия, 414056, Астрахань; Астраханский государственный технический университет; магистрант кафедры эксплуатации водного транспорта; [email protected].
Нгуен Конг Доан — Вьетнам, Ханой; Университет транспортных технологий; канд. техн. наук; зав. кафедрой судовых энергетических установок; [email protected].
