**4. The study results of the influence of the combined heating system different options on engine thermal development indicators**

The general process of pre-start and after-start heating (PSASH) during engine and vehicle operation can be split into the following components: pre-start and after-start processes of thermal development and industrial (commercial) process of the ICE and vehicle operation. The engine pre-start heating without actual start and the operation of the engine in an idling mode can be only realized using the developed heating system. It is a set of subsystems, elements and means of thermal development and maintenance of the thermal state of the engine and the vehicle using the combined heating system based on phase-transitional thermal accumulators. During after-start thermal development of the engine and the vehicle, it is possible to heat them either without using the combined heating system (engine and vehicle standard systems) or using the CHS. During industrial (commercial) process of engine and vehicle operation, the heating system is used only when it is not possible to maintain the thermal state of the engine and the vehicle in a corresponding range under operating conditions. After-start heating of the engine and the vehicle can be carried out in various modes of vehicle operation (both steady and transitional modes of the engine operation when the vehicle is stopped and when in motion). These modes are: (1) heating in an idling mode; (2) heating in an idling mode with electrical consumers switched on; (3) heating in an idling mode with gradual heating in motion; (4) heating in motion. The study of the vehicle heating according to the above-mentioned modes is detailed in [1, 16–19].

The article presents the study results of thermal development of the truck engine 8FS 9.2/8 in operation. The investigation was conducted in the mathematical model of the "combined heating system of the engine and the vehicle" for option 1 - Heating in an idling mode. In evaluating different options of the CSPSH operation the following considerations were taken into account. The combined heating system is a combination of five independent subsystems: the utilization of thermal energy of EG (with TA), rapid heating of the engine, contact thermal accumulator, thermal accumulator for storing motor oil and thermal accumulator for storing a coolant [1, 16–19]. The first two subsystems, working together, provide the work of TA with accelerated circulation of the coolant, motor oil and standard systems of the truck engine 8FS 9.2/8 during pre-start and after-start heating of the truck. Contact thermal accumulator provides long-term storage of accumulated heat in the coolant and motor oil in the cylinder block using an insulated membrane. Thermal accumulator for storing motor oil and thermal accumulator for storing a coolant provide long-term storage of accumulated heat by motor oil and the coolant in separate insulated tanks with TA. The results of pre-start and after-start heating of the engine were assessed and compared in the study depending on the combined heating system different options or their combination.

Based on the developed algorithms for pre-start and after-start heating of the engine coolant and motor oil, 19 combinations of options were suggested to analyze the sets of components of the developed combined heating system (**Table 1**) [1, 2, 5, 12, 15–19]. Thus, for all options during pre-start and after-start heating of the engine with CSPSH mode parameters of its work were estimated. They are as follows: heating the coolant and motor oil from *Т*amb to

**Figure 3.** The flowchart of "combined heating system of the engine and the vehicle."

**Figure 2.** The truck during pre-start and after-start heating of the ICE and the vehicle interior.

108 HVAC System


**# of option The combined heating system components (the definition of the option)**

6 Thermal accumulator for storing motor oil

7 The combination of separate CHS components,

8 The combination of separate CHS components, namely: thermal accumulator + thermal accumulator for storing motor oil (*Т*HАМ *= Тamb*.

9 The combination of separate CHS components, namely: thermal accumulator + thermal

10 The combination of separate CHS components,

TA + CTA + TASMO (*Т*HАМ *= Тamb*.

motor oil (*Т*HАМ *= Тamb*.

and # 6 – TA + TASMO (*Т*HAМ *=* 85°С)

accumulator for storing motor oil (*Т*HAМ *=* 85°С): # 3

namely: thermal accumulator + contact thermal accumulator + thermal accumulator for storing

): # 3, #4 and # 5 –

)

and # 5 – TA + TASMO (*Т*HАМ *= Тamb*.

accumulator (# 3 and # 4): TA + CTA

namely: thermal accumulator + contact thermal

(*Т*HAМ *=* 85°С) – TASMO (*Т*HAМ *=* 85°С)

**Structural and technology features and the use of the combined heating system option** 

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111

The combination of separate components of the combined heating system, namely: phasetransitional thermal accumulator and phasetransitional contact thermal accumulator. # 3 and # 4 describe structural and technology features and the use of the combined heating system option according to its purpose during engine pre-start and after-start heating and long-term keeping in an idling mode without the operation.

The combination of separate components of the combined heating system, namely: phasetransitional thermal accumulator and thermal accumulator for storing motor oil without HAM

describe structural and technology features and the use of the combined heating system option according to its purpose during engine pre-start and after-start heating and long-term keeping in an idling mode without the operation.

The combination of separate components of the combined heating system, namely: phasetransitional thermal accumulator and thermal accumulator for storing motor oil with HAM thermal development (*Т*HAМ *=* 85°С). # 3 and # 6 describe structural and technology features and the use of the combined heating system option according to its purpose during engine pre-start and after-start heating and long-term keeping in an idling mode without the operation.

The combination of separate components of the combined heating system, namely: phase-transitional thermal accumulator, phase-transitional contact thermal accumulator and thermal accumulator for storing motor oil without HAM thermal development

). # 3, # 4 and # 5 describe structural and technology features and the use of the combined heating system option according to its purpose during engine pre-start and after-start heating and long-term keeping in an idling mode without the operation.

(*Т*HАМ *= Тamb*.

). # 3 and # 5

thermal development (*Т*HАМ *= Тamb*.

Engine pre-start and after-start heating is impossible to do. The maintenance of *Т*МО > or ≈ 50°C of the engine with TASMO when the engine is not running is possible with the elements of lubrication system of the engine with thermal accumulator for storing motor oil with HAM thermal development (*Т*HAМ *=* 85°С). To ensure the maintenance of *Т*<sup>c</sup> ≈ 50°C when the engine is not running, the elements of cooling system of the standard engine can only be used.

**according to its purpose**

Improving the Vehicular Engine Pre-Start and After-Start Heating by Using the Combined…

): # 3

)


in an idling mode without the operation.

**# of option The combined heating system components (the definition of the option)**

110 HVAC System

2 Engine standard systems with the combined heating system—SS with the CHS

4 Phase-transitional contact thermal accumulator—CTA

5 Thermal accumulator for storing motor oil

) – TASMO (*Т*HАМ *= Тamb*.

)

(*Т*HАМ *= Тamb*.

3 Phase-transitional thermal accumulator—TA Engine pre-start and rapid after-start

1 2 3 1 Engine standard systems without the combined heating system—SS without the CHS

**Structural and technology features and the use of the combined heating system option** 

Engine pre-start heating is impossible to do. After-start heating is carried out by the elements of cooling and lubrication systems of the standard engine. To ensure the maintenance of *Т*<sup>c</sup> ≈ 50°C and *Т*МО ≈ 50°C when the engine is not running, the elements of cooling and lubrication systems of the standard engine can only be used.

Engine pre-start heating is impossible to do. For rapid after-start heating, only additional electric modulating pumps for the coolant and motor oil of the rapid heating of the engine subsystem are used. To ensure the maintenance of *Т*<sup>c</sup> ≈ 50°C and *Т*МО ≈ 50°C when the engine is not running, the elements of cooling and lubrication systems of the standard engine can only be used.

heating is carried out by phase-transitional TA. Besides, additional electric modulating pumps for the coolant and motor oil of the rapid heating of the engine subsystem (#2), the subsystem of the utilization of thermal energy of EG by phase-transitional thermal accumulator are also used. To ensure the maintenance of *Т*<sup>c</sup> ≈ 50°C and *Т*МО ≈ 50°C of the engine with phase-transitional TA when the engine is not running, additional electric modulating pumps for the coolant and motor oil of the rapid heating of the engine

Engine pre-start and after-start heating is impossible to do. To ensure the maintenance of *Т*<sup>c</sup> > or ≈ 50°C and *Т*МО > or ≈ 50°C of the engine with phase-transitional CTA when the engine is not running, the elements of cooling and lubrication systems of the standard engine can

Engine pre-start and after-start heating is impossible to do. The maintenance of *Т*МО > or ≈ 50°C of the engine with TASMO when the engine is not running is possible with the elements of lubrication system of the engine with thermal accumulator for storing motor oil without HAM thermal development

*Т*<sup>c</sup> ≈ 50°C when the engine is not running, the elements of cooling system of the standard

). To ensure the maintenance of

subsystem can be used.

be used.

(*Т*HАМ *= Тamb*.

engine can only be used.

**according to its purpose**


**# of option The combined heating system components (the definition of the option)**

16 The combination of separate CHS components,

TA + CTA + TASC (*Т*HАМ *= Тamb*.

17 The combination of separate CHS components,

18 The combination of separate CHS components,

storing a coolant (*Т*HАМ *= Тamb*.

19 The combination of separate CHS components,

(*Т*HАМ *=* 85°С)

heating of the truck engine 8FS 9.2/8.

12 – TA + CTA + TASMO+TASC

motor oil (*Т*HАМ *= Тamb*.

a coolant (*Т*HАМ *= Тamb*.

namely: thermal accumulator + contact thermal accumulator + thermal accumulator for storing

namely: thermal accumulator + contact thermal accumulator + thermal accumulator for storing a coolant (*Т*HАМ *=* 85°С): # 3, # 4 and # 13 – TA + CTA + TASC (*Т*HАМ *=* 85°С)

namely: thermal accumulator + contact thermal accumulator + thermal accumulator for storing

namely: thermal accumulator + contact thermal accumulator + thermal accumulator for storing motor oil (*Т*HАМ *=* 85°С) + thermal accumulator for storing a coolant (*Т*HАМ *=* 85°С): # 3, # 4, # 6 and # 13 – TA + CTA + TASMO (*Т*HАМ *=* 85°С) + TASC

) + thermal accumulator for

): # 3, # 4, # 5 and #

**Table 1.** The options of the combined heating system components to analyze the efficiency of pre-start and after-start

): # 3, # 4 and # 12 –

)

**Structural and technology features and the use of the combined heating system option** 

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113

The combination of separate components of the combined heating system, namely: phase-transitional thermal accumulator, phase-transitional contact thermal accumulator and thermal accumulator for storing a coolant without HAM thermal development

The combination of separate components of the combined heating system, namely: phase-transitional thermal accumulator, phasetransitional contact thermal accumulator and thermal accumulator for storing a coolant with HAM thermal development (*Т*HAМ *=* 85°С). # 3, # 4 and # 13 describe structural and technology features and the use of the combined heating system option according to its purpose during engine pre-start and after-start heating and long-term keeping in an idling mode without

The combination of separate components of the combined heating system, namely: phase-transitional thermal accumulator, phase-transitional contact thermal accumulator, thermal accumulator for storing motor oil without HAM thermal development

) and thermal accumulator for storing a coolant without HAM thermal

describe structural and technology features and the use of the combined heating system option according to its purpose during engine pre-start and after-start heating and long-term keeping in an idling mode without the operation.

The combination of separate components of the combined heating system, namely: phase-transitional thermal accumulator, phasetransitional contact thermal accumulator, thermal accumulator for storing motor oil with HAM thermal development (*Т*HAМ *=* 85°С) and thermal accumulator for storing a coolant with HAM thermal development (*Т*HAМ *=* 85°С). # 3, # 4, # 6 and # 13 describe structural and technology features and the use of the combined heating system option according to its purpose during engine pre-start and after-start heating and long-term keeping in an

idling mode without the operation.

). # 3, # 4, # 5 and # 12

). # 3, # 4 and # 12 describe structural and technology features and the use of the combined heating system option according to its purpose during engine pre-start and after-start heating and long-term keeping in an idling mode without the operation.

**according to its purpose**

(*Т*HАМ *= Тamb*.

Improving the Vehicular Engine Pre-Start and After-Start Heating by Using the Combined…

the operation.

(*Т*HАМ *= Тamb*.

development (*Т*HАМ *= Тamb*.


**# of option The combined heating system components (the definition of the option)**

112 HVAC System

11 The combination of separate CHS components,

12 Thermal accumulator for storing a coolant

13 Thermal accumulator for storing a coolant (*Т*HАМ *=* 85°С) – TASC (*Т*HАМ *=* 85°С)

14 The combination of separate CHS components, namely: thermal accumulator + thermal accumulator for storing a coolant (*Т*HАМ *= Тamb*.

15 The combination of separate CHS components, namely: thermal accumulator + thermal

and # 13 – TA + TASC (*Т*HАМ *=* 85°С)

accumulator for storing a coolant (*Т*HАМ *=* 85°С): # 3

and # 12 – TA + TASC (*Т*HАМ *= Тamb*.

(*Т*HАМ *= Тamb*.

namely: thermal accumulator + contact thermal accumulator + thermal accumulator for storing motor oil (ТHAМ = 85°С): # 3, #4 and # 6 – TA + CTA + TASMO (ТHAМ = 85°С)

) – TASC (*Т*HАМ *= Тamb*.

)

**Structural and technology features and the use of the combined heating system option** 

The combination of separate components of the combined heating system, namely: phase-transitional thermal accumulator, phasetransitional contact thermal accumulator and thermal accumulator for storing motor oil with HAM thermal development (ТHAМ = 85°С). # 3, # 4 and # 6 describe structural and technology features and the use of the combined heating system option according to its purpose during engine pre-start and after-start heating and long-term keeping in an idling mode without

Engine pre-start and after-start heating is impossible to do. The maintenance of *Т*<sup>c</sup> > or ≈ 50°C of the engine with TASC when the engine is not running is possible with the elements of cooling system of the engine with thermal accumulator for storing a coolant without HAM thermal development (*Т*HАМ *= Тamb*.

ensure the maintenance of *Т*МО ≈ 50°C when the engine is not running, the elements of lubrication system of the standard engine can

Engine pre-start and after-start heating is impossible to do. The maintenance of *Т*<sup>c</sup> > or ≈ 50°C of the engine with TASC when the engine is not running is possible with the elements of cooling system of the engine with thermal accumulator for storing a coolant with HAM thermal development (*Т*HАМ *=* 85°С). To ensure the maintenance of *Т*МО ≈ 50°C when the engine is not running, the elements of lubrication system of the standard engine can

The combination of separate components of the combined heating system, namely: phasetransitional thermal accumulator and thermal accumulator for storing a coolant without HAM

describe structural and technology features and the use of the combined heating system option according to its purpose during engine pre-start and after-start heating and long-term keeping in an idling mode without the operation.

The combination of separate components of the combined heating system, namely: phasetransitional thermal accumulator and thermal accumulator for storing a coolant with HAM thermal development (*Т*HАМ *=* 85°С). # 3 and # 13 describe structural and technology features and the use of the combined heating system option according to its purpose during engine pre-start and after-start heating and long-term keeping in an idling mode without the operation.

thermal development (*Т*HАМ *= Тamb*.

). To

). # 3 and # 12

**according to its purpose**

the operation.

only be used.

only be used.

): # 3

)

**Table 1.** The options of the combined heating system components to analyze the efficiency of pre-start and after-start heating of the truck engine 8FS 9.2/8.

50°C, min., heating the coolant and motor oil from 50 to 85°C, min., maintaining *Т*<sup>c</sup> ≈ 50°C and *Т*МО ≈ 50°C min. The operating parameters were analyzed separately for the coolant and motor oil at different ambient temperatures, namely 20, 0 and −20°C.

**Figures 4**–**6** show the results of pre-start and after-start heating according to the duration of thermal development of the truck engine coolant and motor oil using the combined heating system. **Figure 4** shows the duration of the coolant and motor oil heating from *Тamb*. to 50°C, min. **Figure 5** shows the duration of the coolant and motor oil heating from 50 to 85°C, min. **Figure 6** shows the duration of maintaining *Т*<sup>c</sup> ≈ 50°С and *Т*МО ≈ 50°С, min. The comparison of indicators for every option of the combined heating system components and the technology for use was provided in absolute values (and in %). Every indicator for a corresponding option was compared with the similar one for a standard system of the engine ZMZ-66-06 (8FS 9.2/8) of the truck GAZ-66-11 (**Figures 4**–**6**). Based on the calculation results of pre-start and after-start heating of the coolant and motor oil according to the appropriate options of the combined heating system components (**Figures 4**–**6**), it is obvious that the use of the above-mentioned ways of heating according to the operating algorithms ensures both pre-start and rapid after-start heating of the engine ZMZ-66-06 (8FS 9.2/8) of the truck GAZ-66-11. It also increases the length of the long stop of the engine without idling. Meanwhile, according to the temperature values of the coolant and motor oil, the engine is in pre-start availability that corresponds to the thermal state to enable the engine load.

The indicators of the engine thermal state during pre-start heating of the coolant and motor oil of the ICE with the combined heating system were compared with the standard systems of the engine (option 1, **Table 1**) from *Тamb*. to 50°C, min (**Figure 4**). The greatest reduction in the heating time was obtained in options 3, 7–11, 14–19 for all ambient temperatures, i.e., at *Тamb*.

**Figure 5.** The influence of options of the combined heating system components on the heating time of the engine coolant

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**Figure 6.** The influence of options of the combined heating system components on the duration of maintaining the

and motor oil from 50 to 85°С.

coolant and motor oil temperatures within ≈50°С.

**Figure 4.** The influence of options of the combined heating system components on the heating time of the engine coolant and motor oil from *Тamb*. to 50°С.

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50°C, min., heating the coolant and motor oil from 50 to 85°C, min., maintaining *Т*<sup>c</sup> ≈ 50°C and *Т*МО ≈ 50°C min. The operating parameters were analyzed separately for the coolant and

**Figures 4**–**6** show the results of pre-start and after-start heating according to the duration of thermal development of the truck engine coolant and motor oil using the combined heating system. **Figure 4** shows the duration of the coolant and motor oil heating from *Тamb*. to 50°C, min. **Figure 5** shows the duration of the coolant and motor oil heating from 50 to 85°C, min. **Figure 6** shows the duration of maintaining *Т*<sup>c</sup> ≈ 50°С and *Т*МО ≈ 50°С, min. The comparison of indicators for every option of the combined heating system components and the technology for use was provided in absolute values (and in %). Every indicator for a corresponding option was compared with the similar one for a standard system of the engine ZMZ-66-06 (8FS 9.2/8) of the truck GAZ-66-11 (**Figures 4**–**6**). Based on the calculation results of pre-start and after-start heating of the coolant and motor oil according to the appropriate options of the combined heating system components (**Figures 4**–**6**), it is obvious that the use of the above-mentioned ways of heating according to the operating algorithms ensures both pre-start and rapid after-start heating of the engine ZMZ-66-06 (8FS 9.2/8) of the truck GAZ-66-11. It also increases the length of the long stop of the engine without idling. Meanwhile, according to the temperature values of the coolant and motor oil, the engine is in pre-start

motor oil at different ambient temperatures, namely 20, 0 and −20°C.

availability that corresponds to the thermal state to enable the engine load.

the engine (option 1, **Table 1**) from *Тamb*.

114 HVAC System

and motor oil from *Тamb*.

to 50°С.

The indicators of the engine thermal state during pre-start heating of the coolant and motor oil of the ICE with the combined heating system were compared with the standard systems of

heating time was obtained in options 3, 7–11, 14–19 for all ambient temperatures, i.e., at *Тamb*.

**Figure 4.** The influence of options of the combined heating system components on the heating time of the engine coolant

to 50°C, min (**Figure 4**). The greatest reduction in the

**Figure 5.** The influence of options of the combined heating system components on the heating time of the engine coolant and motor oil from 50 to 85°С.

**Figure 6.** The influence of options of the combined heating system components on the duration of maintaining the coolant and motor oil temperatures within ≈50°С.

= 20 (0/−20)°C. These options are characterized by the operation of phase-transitional TA and the rapid heating of the engine subsystem at the same time. For relevant temperatures of *Тamb*. = 20 (0/−20)°C, the duration of heating is reduced according to the values 14.4 (24/33.3) min for the coolant and 14.2 (25/35) min for motor oil. This option is compared with the standard systems of the engine (option 1), i.e., 22.8 (31/47.5) min for the coolant and 24.2 (33.3/50.5) min for motor oil. Thus, the duration of heating is reduced by 8.4 (7.1/14.2) min or by 36.9 (22.9/29.9)% for the coolant and by 10 (8.3/15.5) min or by 41.3 (25/30.8) % for motor oil.

**5. Estimating the indicators of optimum temperature (OT) of the** 

The estimation was based on the mathematical modeling of the "combined heating of the engine and the vehicle" system. The mathematical modeling was carried out for various components of the CHS used for the truck and a car. The options of operating conditions and methods of the engine and the vehicle heating were chosen in accordance with the provisions

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The influence of various components of the CHS on pre-start heating of the engine was analyzed in terms of fuel consumption (kg/h). The results revealed the most significant components of the CHS, namely in options 2 and 3. For them, additional estimation studies were carried out to determine the specific indicators of the total influence of the CHS components on the coolant and MO heating time from *Т*amb. to 50°C and from 50 to 85°C. All indicators were compared with thermal development indicators of the engine standard systems. **Figure 7(a)** shows the main indicators of the truck engine thermal development when heating the coolant and MO from *Т*amb. to 50°C. The most significant components of the CHS were studied. They have the greatest influence on thermal processes in the engine coolant and MO. Thus, a phase-transitional TA has the greatest influence on the parameters of the engine coolant heating for all ambient temperatures +20 (0/−20°С) − 0.085 (0.134/0.168) kg/h; and for MO heating, respectively 0.085

To estimate the total influence of the CHS components on the coolant and MO heating time, the most significant components were chosen, namely in options 3–6, 12, 13 and 19 (**Figure 7(b)**. All indicators were compared with the indicators of the engine standard systems. The total influence on thermal development processes implies the total time of pre-start (from *Т*amb. to 50°C) and after-start heating (from 50 to 85°C) and the time of maintaining the coolant and MO temperature within ≈50°C in relation to the fuel consumed for thermal development. **Figure 7b** shows the main study results of the influence of the CHS components on the total time of the coolant and MO thermal development. It is determined in the specific indicators of fuel consumption, kg/h. The lowest fuel consumption indicators were obtained for the CHS with such components: TA + CTA + TASMO (ТHАМ = 85°С) + ТАSC (ТHАМ = 85°С). Phasetransitional TA indicators are worth mentioning as well. They are optimal for all options of the heating, both according to the options of the heating and the ambient temperatures.

In general, to provide the OT of the engine with the CHS, it is advisable to use all options of

To provide the temperature influence on the CC of the EGCS indicators, it is advisable to use TA installed in the exhaust system of the engine. When using TAEGCS, depending on the option of the engine heating, the time of reaching the temperature at the Light-off point (250°С/523 K) of the CC heating curve is 3–5 min of the CC operation for all options. This indicator is almost twice as good as the experimentally obtained indicators of the CC heating. To ensure the compliance with the requirements for the heating periods of different areas of the vehicle interior and the driver, the use of the CHS is completely stipulated. In this case,

simultaneous influence on the coolant and MO.

**engine and the vehicle under operating conditions**

of [1, 5, 10, 11, 16–19].

(0.133/0.167) kg/h.

The indicators of the ICE thermal state during rapid after-start heating of the coolant and motor oil of the engine with the combined heating system were compared with the standard systems of the engine (option 1, **Table 1**) from 50 to 85°С, min (**Figure 5**). The greatest reduction in the heating time was obtained in options 3, 7–11, 14–19 for ambient temperatures at *Тamb*. = 20(0/−20)°C. These options are characterized by the operation of phase-transitional TA and the rapid heating of the engine subsystem at the same time. The duration of heating is reduced according to the values 9.7 (19.2/26.2) min for the coolant and 10.5 (21.2/28.2) min for motor oil. This option is compared with the standard systems of the engine (option 1), i.e., 22.8 (31/47.5) min for the coolant and 24.2 (33.3/50.5) min for motor oil. Thus, the duration of heating is reduced by 13.1 (11.8/21.3) min or by 57.5 (38/44.8)% for the coolant and by 13.7 (12.1/22.3) min or by 57 (36/44.2)% for motor oil.

The duration of maintaining the engine *Т*<sup>c</sup> ≈ 50°С and *Т*МО ≈ 50°С, min (**Figure 6**) within the combined heating system (option 1, **Table 1**) was compared with the standard systems. A substantial increase in long-duration stop of the engine with the combined heating system when the engine was not running in an idling mode was obtained. The duration of maintenance did not change in option 2 for the coolant and motor oil, in options 5 and 6 for the coolant, in options 12 and 13 for motor oil. According to **Figure 6**, the increase in the maintenance duration occurred in options 3–18 for both the coolant and for motor oil for ambient temperatures *Тamb*. = 20 (0/−20)°C. The most significant increase in duration occurred in option 19 for the coolant and motor oil, in options 15 and 17 for the coolant, in options 9 and 11 for motor oil respectively. These options are characterized by simultaneous operation of phase-transitional TA and the rapid heating of the engine subsystem, contact thermal accumulator subsystem as well as thermal accumulator for storing motor oil and thermal accumulator for storing a coolant previously heated to *Т*HAМ *=* 85°С. The duration of maintaining *Т*<sup>c</sup> ≈ 50°С and *Т*МО ≈ 50°С is increased according to the values from 720 (600/510) min to 2410 (2078/1870) min for the coolant and from 720 (600/510) min to 2410 (2078/1870) min for motor oil. This option was compared with the standard systems of the engine (option 1), i.e., 80 (40/20) min for the coolant and 100 (60/30) min for motor oil. Thus, the duration of maintaining the temperatures is increased from 640 (560/490) min. to 2330 (2038/1850) min or ranging from 9 (14/24) to 29.13 (50.95/92.50) times for the coolant and from 620 (540/480) min to 2310 (2018/1840) min or ranging from 6.2 (9/16) to 15.9 (33.63/61.33) times for motor oil for appropriate operating conditions.

The use of the combined heating system is generally effective (**Figures 4**–**6**) for pre-start and after-start thermal development of the vehicular engine and for maintaining it for a long time when it is not running under different climatic conditions. The peculiarities of the combined heating system components and the technology for use are chosen depending on operational needs, climatic conditions and the category of the vehicle.
