**2. Creating the scheme of the ICE and vehicle combined heating system and its operating principle**

To create the ICE and vehicle heating system, a combination of phase-transitional thermal accumulators was used (combination by function). Thermal accumulator is a device for accumulating thermal energy based on physical or chemical process associated with heat absorption and release [1–11]. The main processes are: accumulation-release of internal energy when heating–cooling solids or liquids, phase transitions with absorption-release of latent heat, the process of sorption–desorption or a reverse chemical reaction occurring with heat releaseabsorption. Accumulation of thermal energy or heat accumulation is a process of accumulating thermal energy, when its supply is maximum, for later use when the need arises. The process of accumulating energy is called charging, the process of its use is called discharging [1–5]. Substances used to accumulate thermal energy are called heat accumulating materials. The amount of accumulated energy depends on the temperature at which heat accumulating material is heated and its specific heat capacity. The main operating procedures in thermal accumulators, namely the accumulation of thermal energy, are based on the reverse phasetransitional process of melting-solidification. In this case, phase change material is used as the heat accumulating material. The implementation of this method is more difficult because of the need to make the design more complicated. However, much greater amount of heat per unit of volume is accumulated in such thermal accumulators. The process of charging and discharging can be performed in a narrow temperature range, which is very important when there is a need for thermal accumulators to work at small temperature differences. In vehicles the use of thermal accumulators is advantageous to facilitate the engine start and heating the vehicle interior during cold weather. The heat is accumulated during engine operation and can be stored for several days. To do this, thermal accumulator is placed in a Dewar flask (thermos) which provides the best thermal insulation.

In [1, 2], the main stages of creating the combined heating system (CHS) of the vehicular engine and the vehicle are shown. To ensure the required temperature condition during pre-start and after-start heating of the internal combustion engine (ICE) and the vehicle under cold operating conditions, a scheme and components of the CHS are formed on the basis of vehicular engine main systems. The suggested CHS consists of the following subsystems: rapid heating of the engine (RHE), the utilization of thermal energy of exhaust gases (EG) by phase-transitional TA (UTETA), contact thermal accumulator (CTA), thermal accumulator for storing motor oil (TASMO), thermal accumulator for storing a coolant (TASC), TA of EG cleaning system (TAEGCS). The CHS itself is a part of a cooling system (CS), lubrication system (LS) and exhaust system of the vehicular engine. It performs some functions of the systems and has a significant influence on the operation of the vehicular engine [1–4]. It is the CHS that provides pre-start and rapid after-start heating of a coolant and motor oil, exhaust gases cleaning system (EGCS) of the engine to the temperature at which the engine can be loaded and then to an operating temperature. The operating temperature is maintained for a long time within specified limits.

both at the system level and at the component level. These suggested methods are particularly relevant to those modes of vehicular engines that require significant efforts for their thermal development under cold operating conditions. They are as follows: pre-start and after-start heating of the engine, keeping the engine heated for a successful start under cold operating conditions. Apart from ease of use, the decisive factors are low cost of devices for engine thermal development, state legislation and standards, the need for full power immediately after the engine starts, improved fuel economy and reduced emissions during pre-start and after-start thermal development. The limiting factors are weight and size characteristics of the devices and their compact installation space according to modern vehicle design. In this regard, the most relevant is the development of complex systems for solving these problems in both the design of the engine and the vehicle. In this case one of the promising ways is the development and the study of the combined heating system with phase-transitional thermal accumulator (TA) to carry out pre-start and after-start heating of the engine under cold operating conditions.

**2. Creating the scheme of the ICE and vehicle combined heating** 

To create the ICE and vehicle heating system, a combination of phase-transitional thermal accumulators was used (combination by function). Thermal accumulator is a device for accumulating thermal energy based on physical or chemical process associated with heat absorption and release [1–11]. The main processes are: accumulation-release of internal energy when heating–cooling solids or liquids, phase transitions with absorption-release of latent heat, the process of sorption–desorption or a reverse chemical reaction occurring with heat releaseabsorption. Accumulation of thermal energy or heat accumulation is a process of accumulating thermal energy, when its supply is maximum, for later use when the need arises. The process of accumulating energy is called charging, the process of its use is called discharging [1–5]. Substances used to accumulate thermal energy are called heat accumulating materials. The amount of accumulated energy depends on the temperature at which heat accumulating material is heated and its specific heat capacity. The main operating procedures in thermal accumulators, namely the accumulation of thermal energy, are based on the reverse phasetransitional process of melting-solidification. In this case, phase change material is used as the heat accumulating material. The implementation of this method is more difficult because of the need to make the design more complicated. However, much greater amount of heat per unit of volume is accumulated in such thermal accumulators. The process of charging and discharging can be performed in a narrow temperature range, which is very important when there is a need for thermal accumulators to work at small temperature differences. In vehicles the use of thermal accumulators is advantageous to facilitate the engine start and heating the vehicle interior during cold weather. The heat is accumulated during engine operation and can be stored for several days. To do this, thermal accumulator is placed in a Dewar flask

In [1, 2], the main stages of creating the combined heating system (CHS) of the vehicular engine and the vehicle are shown. To ensure the required temperature condition during pre-start and

**system and its operating principle**

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(thermos) which provides the best thermal insulation.

The elements of the combined heating system, such as the subsystems of rapid heating of the engine, the utilization of thermal energy of exhaust gases by phase-transitional TA, contact thermal accumulator and thermal accumulator for storing a coolant are the components of the engine cooling system. TA of EG cleaning system is a component of the engine exhaust system. The elements of the combined heating system, such as the subsystems of rapid heating of the engine, the utilization of thermal energy of exhaust gases by phase-transitional TA, contact thermal accumulator and thermal accumulator for storing motor oil are the components of the engine lubrication system. All the above-mentioned subsystems can work together within and according to the algorithm of the combined heating system operation or separately from each other performing their inherent functions [1, 5].

The combined heating system generally works on the principle of thermal energy of EG accumulation by phase-transitional thermal accumulator of the utilization of thermal energy of EG subsystem. It also implies the accumulation of engine thermal energy by contact thermal accumulator in the form of convection and thermal radiation of the vehicular engine during its operation. The "free" thermal energy generated during the fuel combustion is emitted into the atmosphere and is not used usefully.

**Figure 1** shows the implementation of the combined heating system for the vehicular engine. EG thermal energy accumulation of the vehicular engine 1 by phase-transitional thermal accumulator, namely by the subsystem of the utilization of thermal energy of exhaust gases 20, is made possible by parallel installing the engine silencer 18 in the EG heat exchanger (HE) 6. The circulation of a heat carrier between TA 20 and exhaust gases heat exchanger 6 is provided by a modulating pump 21. The heat carrier passing through HE 6 in the exhaust manifold is heated by thermal energy of EG to a temperature of 150–190°C (a process fluid with a boiling point of 220°C was used as the heat carrier). Heat exchanger 6 is installed in a bypass, in parallel with the main EG manifold of the vehicular engine. Such a decision was made in order to ensure the disconnection of the heat exchanger 6 after phase-transitional TA 20 of the subsystem of the utilization of thermal energy is fully charged. The switching of EG flow is carried out by electromagnetic gas valves 30 and 25 with an electric drive based on control system commands. The EG flow adjustment is carried out following a special algorithm [4, 9, 10] according to a developed cycle of heating the engine. From the heat exchanger 6 the heat carrier delivers the heat into phase-transitional TA 20 of the subsystem of the utilization of thermal energy. In an

Using contact thermal accumulator 17 does not require significant changes in the design of the vehicular engine and its systems. It is easily installed, is easy to maintain and does not require additional energy. The contact thermal accumulator operation is based on the change of the phase state of heat accumulating material when the energy is emitted and absorbed during convection and thermal radiation of the cylinder block and the engine oil pan. Due to contact thermal accumulator, an insulating function of the engine is performed and the minimum loss of thermal energy in the form of convection and thermal radiation is achieved during engine operation. In this way it is also possible to avoid thermal stresses in the engine during its heating at low temperatures. The contact thermal accumulator operation provides a long-term maintenance of the set coolant and motor oil temperatures when the engine is switched off,

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The peculiarity of the thermal accumulator for storing motor oil design 19 (**Figure 1**) is an additional phase-transitional contact TA in an accumulation vessel membrane for motor oil. It is similar in design and operating principle to contact thermal accumulator 17, but is mounted on the accumulation vessel case for draining motor oil. Due to thermal accumulator for storing motor oil 19 the minimum loss of thermal energy is achieved. It is released by motor oil after its draining by electromagnetic hydraulic valves 28 and 29 in the insulated vessel with TA during long-term stop of the vehicular engine. When motor oil is pumped backwards into the engine oil pan by the modulating pump 24 it is possible to rapidly heat the engine components and lubrication system parts. They are as follows: a crankshaft area, an oil channel and an oil case of the vehicular engine. The motor oil temperature in thermal accumulator for

The peculiarity of the thermal accumulator for storing a coolant design 9 (**Figure 1**) is an additional phase-transitional contact TA in the accumulation vessel membrane for the coolant. It is similar in design and operating principle to thermal accumulator for storing a coolant 19, but is mounted on the accumulation vessel case for draining the coolant. Due to thermal accumulator for storing a coolant 9 the minimum loss of thermal energy is achieved. It is released by the coolant after its draining by electromagnetic hydraulic valves 10 and 11 in the insulated vessel 9 with TA during long-term stop of the vehicular engine. When the coolant is pumped backwards into the engine cooling system by the modulating pump 8 it is possible to rapidly heat the engine components and cooling system parts. They are as follows: a coolant case and the ICE cylinder head. The coolant temperature in thermal accumulator for storing a

EG thermal energy for rapid heating of a catalytic converter 5 in the exhaust system is accumulated in TA of exhaust gases cleaning system during engine operation. A rapid heating of catalytic converter composition 5 after starting the engine occurs when EG pass through TA

The interior of the vehicle is heated by the heat exchanger 7 during engine operation when the

In addition to the above-mentioned components, the combined heating system also includes standard components of the engine and its cooling and lubrication systems (**Figure 1**). They are as follows: a cooling system radiator 2, an engine output shaft 3 an intake manifold 4, EG

unlike the well-known TA by means of which the ICE is heated after stop [1, 5, 9].

storing motor oil 19 is controlled by the built-in motor oil temperature sensor.

coolant 9 is controlled by the built-in coolant temperature sensor.

coolant circulates in the engine cooling system through the heat exchanger.

of exhaust gases cleaning system.

**Figure 1.** The scheme of the combined heating system of the engine and the vehicle, and specifications of phasetransitional TA and its HAM.

insulated tank of TA with three heat exchangers (for TA charging and heating of the engine coolant and motor oil) the heat carrier cools down and gives off the accumulated thermal energy to a phase-transitional heat accumulating material (HAM).

In the process of HAM energy accumulation the most efficient is the process of a phase transition of the material (TA filler), i.e., the change of its physical state which requires a large amount of EG energy. The most energy-intensive process is the phase transition of HAM. All the other processes of HAM energy accumulation do not require such a large amount of energy. The peculiarities of phase-transitional TA 20 at different periods of thermal energy accumulation and release are detailed in [1, 5, 10, 11].

Contact thermal accumulator 17 of the vehicular engine (**Figure 1**) is a multi-layered case. To ensure close fitting it is mounted on the outside of the cylinder block and the engine oil pan [8]. The peculiarity of the contact thermal accumulator design 17 is the availability of individual sections of container-based phase-transitional HAM that are fitted to the outside of the cylinder block and the oil pan. They are covered by several layers of thermal insulation material [1, 5, 9]. Using contact thermal accumulator 17 does not require significant changes in the design of the vehicular engine and its systems. It is easily installed, is easy to maintain and does not require additional energy. The contact thermal accumulator operation is based on the change of the phase state of heat accumulating material when the energy is emitted and absorbed during convection and thermal radiation of the cylinder block and the engine oil pan. Due to contact thermal accumulator, an insulating function of the engine is performed and the minimum loss of thermal energy in the form of convection and thermal radiation is achieved during engine operation. In this way it is also possible to avoid thermal stresses in the engine during its heating at low temperatures. The contact thermal accumulator operation provides a long-term maintenance of the set coolant and motor oil temperatures when the engine is switched off, unlike the well-known TA by means of which the ICE is heated after stop [1, 5, 9].

The peculiarity of the thermal accumulator for storing motor oil design 19 (**Figure 1**) is an additional phase-transitional contact TA in an accumulation vessel membrane for motor oil. It is similar in design and operating principle to contact thermal accumulator 17, but is mounted on the accumulation vessel case for draining motor oil. Due to thermal accumulator for storing motor oil 19 the minimum loss of thermal energy is achieved. It is released by motor oil after its draining by electromagnetic hydraulic valves 28 and 29 in the insulated vessel with TA during long-term stop of the vehicular engine. When motor oil is pumped backwards into the engine oil pan by the modulating pump 24 it is possible to rapidly heat the engine components and lubrication system parts. They are as follows: a crankshaft area, an oil channel and an oil case of the vehicular engine. The motor oil temperature in thermal accumulator for storing motor oil 19 is controlled by the built-in motor oil temperature sensor.

The peculiarity of the thermal accumulator for storing a coolant design 9 (**Figure 1**) is an additional phase-transitional contact TA in the accumulation vessel membrane for the coolant. It is similar in design and operating principle to thermal accumulator for storing a coolant 19, but is mounted on the accumulation vessel case for draining the coolant. Due to thermal accumulator for storing a coolant 9 the minimum loss of thermal energy is achieved. It is released by the coolant after its draining by electromagnetic hydraulic valves 10 and 11 in the insulated vessel 9 with TA during long-term stop of the vehicular engine. When the coolant is pumped backwards into the engine cooling system by the modulating pump 8 it is possible to rapidly heat the engine components and cooling system parts. They are as follows: a coolant case and the ICE cylinder head. The coolant temperature in thermal accumulator for storing a coolant 9 is controlled by the built-in coolant temperature sensor.

insulated tank of TA with three heat exchangers (for TA charging and heating of the engine coolant and motor oil) the heat carrier cools down and gives off the accumulated thermal

**Figure 1.** The scheme of the combined heating system of the engine and the vehicle, and specifications of phase-

In the process of HAM energy accumulation the most efficient is the process of a phase transition of the material (TA filler), i.e., the change of its physical state which requires a large amount of EG energy. The most energy-intensive process is the phase transition of HAM. All the other processes of HAM energy accumulation do not require such a large amount of energy. The peculiarities of phase-transitional TA 20 at different periods of thermal energy

Contact thermal accumulator 17 of the vehicular engine (**Figure 1**) is a multi-layered case. To ensure close fitting it is mounted on the outside of the cylinder block and the engine oil pan [8]. The peculiarity of the contact thermal accumulator design 17 is the availability of individual sections of container-based phase-transitional HAM that are fitted to the outside of the cylinder block and the oil pan. They are covered by several layers of thermal insulation material [1, 5, 9].

energy to a phase-transitional heat accumulating material (HAM).

accumulation and release are detailed in [1, 5, 10, 11].

transitional TA and its HAM.

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EG thermal energy for rapid heating of a catalytic converter 5 in the exhaust system is accumulated in TA of exhaust gases cleaning system during engine operation. A rapid heating of catalytic converter composition 5 after starting the engine occurs when EG pass through TA of exhaust gases cleaning system.

The interior of the vehicle is heated by the heat exchanger 7 during engine operation when the coolant circulates in the engine cooling system through the heat exchanger.

In addition to the above-mentioned components, the combined heating system also includes standard components of the engine and its cooling and lubrication systems (**Figure 1**). They are as follows: a cooling system radiator 2, an engine output shaft 3 an intake manifold 4, EG temperature sensor 12; a lubrication system radiator 13; gas analysis equipment 14 (in the form of appropriate sensors); a tank for expanding the heat carrier 15; EG temperature sensor 16. The circulation of the coolant and motor oil in the combined heating system is provided by modulating pumps 22 and 23. The coolant and motor oil regulation is provided by electromagnetic hydraulic valves 26 and 27.

heating of the working engine up to the coolant and motor oil temperatures at +85°C. This is achieved due to further use of the accumulated heat in TA and thermal energy from the working engine. After reaching the coolant and motor oil temperatures of +85°C, the combined heating system maintains it within the limits set, i.e., 85 ± 5°C and then the engine standard system (SS) starts working (in the meanwhile, the combined heating system stops working). Taking into consideration the data from temperature sensors, the control system of the combined heating system calculates the optimal rotational speed of circulation pumps 21, 22, 23. It gives commands to the system valves directing the flow of working fluids through certain CSPSH elements. The combined heating system functioning is based on the analysis of tem-

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During a stop and storage of the heat accumulated by contact thermal accumulator 17 of the engine being shut off, the contact thermal accumulator operation implies giving off HAM phase-transitional heat of contact thermal accumulator backwards to provide long-term maintenance of the coolant and motor oil temperatures. In low ambient temperature and when phase-transitional TA 20 for the utilization of thermal energy of exhaust gases subsystem is charged, when the heat accumulated by contact thermal accumulator 17 is insufficient,

During a long stop of the engine, when it is necessary to maintain the coolant and motor oil within the "hot heating" for a long time, thermal accumulator for storing motor oil 19 and (or) thermal accumulator for storing a coolant 9 are used (**Figure 1**), in which the coolant and motor oil are drained from lubrication system and cooling system of the engine. If it is necessary to start the engine when phase-transitional TA 20 for the utilization of thermal energy of exhaust gases subsystem is charged, thermal accumulator for storing motor oil (thermal accumulator for storing a coolant) is combined with lubrication system (cooling system) of the engine by using valves 28 and 29 (9 and 11). By using the circulation pump 24 (8), motor oil (the coolant) goes to the engine cylinder block. Further heating of the engine 1 is carried out similarly as described above. By using motor oil and coolant temperature sensors, working capacity of the combined heating system is controlled in relation to heat capacity of its

The research on using the CHS in vehicles was based both on experiments and numerical

The results of experimental studies conducted by the authors under the ITS information conditions are detailed in [1, 5, 10, 11–13] (**Figure 2**). The authors developed a mathematical model [1, 5, 10, 11–13] for the estimation studies (**Figure 3**). It is based on a systems approach used in the processes of the vehicular thermal development when using phase-transitional

perature values of the coolant and motor oil heat carriers [1, 5, 10, 11].

the engine 1 heating is carried out similarly as described above.

components and subsystems and its further use.

**3. Objects of experimental studies**

thermal accumulators [1, 4–19].

modeling.

Pre-start and after-start heating of the coolant and motor oil is possible with standard heating of the engine and (or) in the following modes of the combined heating system operation. The examples are: when operating only the rapid heating of the engine subsystem in the process of after-start heating of the engine, when operating the rapid heating of the engine subsystem with the utilization of thermal energy of exhaust gases by phase-transitional TA, the combined functions of contact thermal accumulator (thermal accumulator for storing motor oil and (or) thermal accumulator for storing a coolant) or joint operation of contact thermal accumulator + thermal accumulator for storing motor oil + thermal accumulator for storing a coolant and the utilization of thermal energy of exhaust gases by phase-transitional TA. Storing thermal energy, accumulated by the coolant and motor oil, is possible with standard ICE assembly and (or) in the following modes of the combined heating system operation. The examples are: when operating the rapid heating of the engine subsystem with the utilization of thermal energy of exhaust gases by phase-transitional TA, when operating only contact thermal accumulator or thermal accumulator for storing motor oil (thermal accumulator for storing a coolant), the combined functions of contact thermal accumulator (thermal accumulator for storing motor oil and (or) thermal accumulator for storing a coolant) or joint operation of contact thermal accumulator + thermal accumulator for storing motor oil + thermal accumulator for storing a coolant and the utilization of thermal energy of exhaust gases by phase-transitional TA.

If it is necessary to start the engine after a long stop, the combined heating system is involved. It works according to its own algorithms and includes electric modulating pumps 21, 22, 23 of the rapid heating of the engine subsystem. They circulate the coolant and motor oil in the vehicular engine and phase-transitional TA for the utilization of thermal energy of exhaust gases. Passing through TA, the coolant gets thermal energy accumulated by HAM and transfers it by the coolant to the engine cooling system and by motor oil to the lubrication system and to the engine design elements. The right choice of TA 20 thermal capacity allows you to quickly heat the ICE from low ambient temperature (−20°C) to the coolant and motor oil temperatures at +40–60°C. The choice of TA thermal capacity by HAM weight is based on a calculation of the heat balance of the engine with the combined heating system and the vehicle. It helps determine the amount of thermal energy required for heating the coolant and motor oil, cylinder block, cylinder head, connecting branch pipes and manifolds considering heat loss [1, 5, 10, 11].

After receiving thermal energy from the coolant and motor oil, the engine elements transfer it to the combustion chamber. It positively affects the process of ICE start which occurs after the combined heating system sensors record the coolant and motor oil temperatures at +40– 60°C. After that the ICE starts running and it is possible to load the engine. After starting the ICE, the combined heating system continues its work and facilitates more rapid and efficient heating of the working engine up to the coolant and motor oil temperatures at +85°C. This is achieved due to further use of the accumulated heat in TA and thermal energy from the working engine. After reaching the coolant and motor oil temperatures of +85°C, the combined heating system maintains it within the limits set, i.e., 85 ± 5°C and then the engine standard system (SS) starts working (in the meanwhile, the combined heating system stops working).

Taking into consideration the data from temperature sensors, the control system of the combined heating system calculates the optimal rotational speed of circulation pumps 21, 22, 23. It gives commands to the system valves directing the flow of working fluids through certain CSPSH elements. The combined heating system functioning is based on the analysis of temperature values of the coolant and motor oil heat carriers [1, 5, 10, 11].

During a stop and storage of the heat accumulated by contact thermal accumulator 17 of the engine being shut off, the contact thermal accumulator operation implies giving off HAM phase-transitional heat of contact thermal accumulator backwards to provide long-term maintenance of the coolant and motor oil temperatures. In low ambient temperature and when phase-transitional TA 20 for the utilization of thermal energy of exhaust gases subsystem is charged, when the heat accumulated by contact thermal accumulator 17 is insufficient, the engine 1 heating is carried out similarly as described above.

During a long stop of the engine, when it is necessary to maintain the coolant and motor oil within the "hot heating" for a long time, thermal accumulator for storing motor oil 19 and (or) thermal accumulator for storing a coolant 9 are used (**Figure 1**), in which the coolant and motor oil are drained from lubrication system and cooling system of the engine. If it is necessary to start the engine when phase-transitional TA 20 for the utilization of thermal energy of exhaust gases subsystem is charged, thermal accumulator for storing motor oil (thermal accumulator for storing a coolant) is combined with lubrication system (cooling system) of the engine by using valves 28 and 29 (9 and 11). By using the circulation pump 24 (8), motor oil (the coolant) goes to the engine cylinder block. Further heating of the engine 1 is carried out similarly as described above. By using motor oil and coolant temperature sensors, working capacity of the combined heating system is controlled in relation to heat capacity of its components and subsystems and its further use.
