Experimental study of dual-cycle thermal management system for engineering radiator | Scientific Reports

Scientific Reports volume 14, Article number: 19691 (2024) Cite this article

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With the increasing demand for heat dissipation of engineering vehicles, a dual-cycle cooling system is introduced in this paper to prevent the adverse effects of engineering vehicles’ equipment when operating at the overheating temperature. The performance of the new system is analyzed through tests, and the results show that the dual-cycle cooling system can meet the thermal balance requirements of the engineering vehicle during the shovel operation. Compared with the traditional cooling system, the new cooling system improved performance in terms of volume, engine energy consumption and working oil efficiency. The oil consumption of a wheel loader using the dual-cycle cooling system is reduced by 1% per hour, and the temperature of its transmission oil and hydraulic oil is reduced by more than 10 °C. The new cooling system has bright future in energy saving and emission reduction of engineering vehicles.

Since twenty-first century, the rapid economic development has led to the depletion of oil resources. At present, new energy engines with technical bottlenecks cannot completely replace internal combustion engines. Therefore, the demand for developing energy-saving and environmental protection engines is urgent. As vehicle thermal management, it is a feasible method to improve engine combustion performance and reduce pollutant emissions by improving the performance of cooling system1,2,3,4.

For the traditional cooling system, Pang H, Ap N S and Lin et al.5,6,7 gave a comprehensive and detailed introduction to the traditional engine cooling system. Klett et al.8 designed a heavy-duty vehicle heat exchanger made of high thermal conductivity graphite material, which has twice the heat transfer coefficients of conventional heat sinks. Ng et al.9 conducted wind tunnel and road tests of vehicle at high blockage ratio, aiming to improve the cooling capacity of the cooling system.

However, traditional cooling systems can no longer meet the cooling requirements of modern engines, such as turbocharged engine. Obidi et al.10 evaluated the engine performance, fuel economy, safety and reliability, aerodynamics of the thermal management system for heavy trucks, and proposed new thermal management concepts. Chanfreau et al.11 introduced the advanced engine cooling strategy and verified the advantages of the advanced cooling system in fuel economy and emission through experiments.

With the development of electronic technology and control technology, some scholars have designed new electronic cooling system. Shin et al.12 designed an electromagnetic clutch pump to avoid excessive cooling of the engine cooling system, at the same time, shorten engine warm-up time, reduce fuel consumption and pollutant emissions. Brace et al.13 designed a cooling system equipped with an advanced electronic water pump with flow control function, and its performance was simulated. The results showed that the system can improve fuel economy. Choukroun et al.14 designed an electronic cooling circuit controlled by an electronic controller to make the engine temperature rise faster during cold start-up. Page et al.15 described a thermal management system for army vehicles consisting of electric coolant pump, fan, electronic control valve, multiple air-cooled heat exchangers, and electronic control system. Compared with vehicles using traditional thermal management system, the new thermal management system can improve the performance of transmission system and make the vehicle more fuel efficient. Setlur et al. and Wagner et al. 16,17 designed a controller based on non-linear control strategy for electronic cooling system. The experimental results showed that the controller can keep the engine cooling system temperature near the target value under various working conditions.

Some experts and scholars have carried out simulation research on the cooling system. Cho et al.18 modeled the cooling system of pickup truck by the software GT-Cool, and verified the correctness of the cooling system model with traditional mechanical cooling pump by experimental data. The model of mechanical pump was replaced by the model of electronic pump. The simulation results showed that the cooling system with electronic pump can reduce the radiator volume without losing cooling performance. Zhao et al.19 proposed a simulation method considering the flow and heat transfer of coolant for engine cooling system, and simulated the cooling system of a certain tank. The results agreed well with the experimental data. Staunton et al.20 used one-dimensional simulation software to model and simulate the energy-saving potential of different types of advanced thermal management systems topologies. The simulation results showed that all-electric cooling system cannot be applied to low-voltage electric system vehicles.

In order to improve the performance of the cooling system, some scholars propose to divide the single circuit of the traditional cooling system into two independent cooling circuits. Chalgren et al.21,22,23,24,25 proposed an advanced thermal management solution for trucks with two cooling circuits. The first cooling circuit consists of electric water pump, electric thermostat, and electric fan. The second cooling circuit is used to drive the system. This solution can improve the efficiency of engine compartment space utilization and the air mobility at the engine compartment.

At present, scholars' research on the cooling system is mainly focused on the engine of automobile or battery of electric vehicle. However, there are few studies on the application of loader cooling systems and the solution of dividing the loader cooling system into two cooling circuits is not well known. Due to the harsh working environment, large working load, high power and large heat production, the heat dissipation performance of the loader radiator is higher. Currently, there is a lack of research on the loader of the dual cooling circuit cooling system.

In view of the above situation, this paper proposes a dual-cycle cooling system for engineering vehicles. The purpose is to improve the overall efficiency of the engine (increasing its cooling capacity) and power (enhancing the ability to cool the charge air) under stable operating conditions of the vehicle, and to improve the utilization efficiency of the working oil (reducing the cooling temperature of the hydraulic oil and the transmission oil). Ultimately, the goal of reducing fuel consumption and pollutant emissions is achieved. Combined with all these thermal requirements, the traditional air-cooled radiator is hard to meet these demands. These different levels of heat demand do not properly match each other. A dual-cycle cooling system allows for reorganization of all these thermal requirements in order to more effectively connect different functions. Therefore, this paper took a wheel loader to conduct tests on the conventional cooling system and the new dual-cycle cooling system, and the inlet and outlet temperature of each radiator and fuel consumption of the loaders was collected. The performance of the dual temperature system was evaluated, the location of various heat exchangers was changed, and the possibilities associated with different component layouts were explored, focusing on the improvement in thermal transient behavior due to the dual cycle cooling system.

The power of wheel loader is mainly provided by the diesel engine whose efficiency is generally less than 35%, and the cooling loss accounts for about 30% of the total fuel energy. According to the combustion thermochemistry and engine bench test data of main engine plant, the preliminary calculation of the torque and power point energy distribution of a wheel loader is shown in Table 1. It can be seen from Table 2 that the heat source of wheel loader has a large temperature difference, and the demand for heat exchange is also different. It can be seen from Tables 1 and 2 that coolant total absorption is 179.7 kW. The cooling system should have a heat exchange capacity of about 180 kW to maintain the thermal balance of the whole vehicle.

The conventional loader cooling system has only one cooling circuit, which is generally composed of two parts: a cooling medium and a cooling drive. The cooling medium includes coolant, air, engine oil, transmission oil, and hydraulic oil. During the coolant flows out of the radiator and cools the engine, the coolant is heated and flows back to the radiator. The transmission oil radiator, hydraulic oil radiator and turbocharged intercooler are air-cooled radiators, whose heat dissipation capability just depends on air flow. The flow pattern is shown in Fig. 1.

Schematic diagram of the traditional cooling system.

Unlike conventional cooling systems, the dual-cycle cooling system uses water to cool the transmission oil, hydraulic oil, and compressed air. According to the heat generated by heat source, the principle of the dual-cycle cooling system is cooling the high and low temperature heat sources respectively, as shown in Fig. 2. The specific implementation measures for high and low temperature heat source separation and cooling are as follows: the high temperature cycle in the dual-cycle cooling system is used to cool the engine and transmission oil, and the low temperature cycle is used to cool the hydraulic oil coolant and intercooler coolant. The low temperature cycle is driven by a independent water pump.

Schematic diagram of dual-cycle cooling system.

In the high-temperature cycle, the coolant is cooled by the fan, and enters the transmission oil radiator to cool the transmission oil, then flows through the engine body water jacket. In the low-temperature cooling cycle, the coolant is cooled by the fan too, and the coolant flows through the water-cooled intercooler to cool the compressed air, then enters the hydraulic oil radiator. The loader system model layout diagram of the dual-cycle cooling system is shown in Fig. 3.

Schematic diagram of the dual-cycle cooling system model.

In order to study the working characteristics of the dual-cycle cooling system, field tests under the typical working conditions of shoveling operation were carried out on the wheel loader. The technical parameters of the machine are shown in Table 3. The ambient temperature is 35 °C and the pavement is hard sand road surface The V-type continuous shovel loading operation maintains the throttle opening state, and the bucket full bucket rate is not less than 95%. The test data is recorded by the sensor and data acquisition module. The technical parameters of the machine are shown in Table 3.

The acquisition equipment used in the test includes data acquisition module, thermocouple sensor, data recorder, etc. The technical parameters of some equipment are as follows:

Data acquisition instrument: DEWE-43-A, a total of 18 signal channels, including 8 analog signal input channels, sampling frequency 1000 Hz.

Temperature sensor: (I) Omega’s TC-T-NPT-72 series temperature sensor is used, and the maximum measurement temperature can reach 650 °C. (II) 5TC series temperature sensor can withstand up to 180 °C, both temperature sensors are thermocouple type.

Test equipments and measuring point sensors arrangement are shown in Figs. 4, 5 and 6. The temperature sensor is used to measure the inlet and outlet temperature of engine coolant, hydraulic oil heat exchanger and transmission oil heat exchanger. Each sensor is connected to the data acquisition module through a data line, and uses computer to store data. Figure 5 shows the location of each sensor when testing a dual-cycle cooling system, and Table 4 indicates the measurement parameters for each sensor. At the end of temperature collection, 33 times of shovel loading fuel consumption tests were carried out.

Acquisition module and sensors.

The engine compartment of wheel loaders.

Location of each sensor.

After 100 min of continuous operation, the new cooling systems reached thermal equilibrium. The equilibrium temperature of each measuring point is shown in Table 5. Under the same environmental conditions, the systems achieve heat dissipation requirements of the various heat sources of the loader. However, compared with the test data of the traditional cooling system, it can be found that the cooling capacity of each radiator in the dual-cycle cooling system is stronger than that of the traditional cooling system. The temperature drop between intercoolers is increased by 2 °C. The temperature drop between the hydraulic pressure is increased by 12 °C. The inlet temperature of the transmission oil is also reduced by 20 °C. Under the full load of the loader, the dual-cycle cooling system can dissipate more quantity of heat, and ensure the loader systems under a suitable temperature environment, avoiding overheating of the loader.

In the wheel loader thermal-equilibrium state, the engine radiator inlet and outlet experimental data of the conventional cooling system (TC) and the dual-cycle cooling system (DC) within 55 min are extracted, as shown in Fig. 7. At the same time, the outlet and inlet temperatures of the water tank in the dual-cycle cooling system are lower than those in the traditional cooling system. The cooling temperature difference of the double cycle cooling system is more than 3 °C. Good cooling capacity can make the engine run in the optimum temperature range, thus making the fuel combustion more fully, and ultimately achieving the purpose of improving the engine performance.

Temperature of engine radiator.

As is shown in Fig. 8, the inlet and outlet temperature of the hydraulic oil within 55 min are collected from the heat exchangers in the traditional cooling system (TC) and the dual-cycle cooling system (DC). Working for a long time under high temperature and pressure, the hydraulic oil will deteriorate rapidly, which makes the hydraulic system easy to leak and reduce its working efficiency. Compared to the conventional cooling system, when the hydraulic oil passes through the hydraulic oil radiator in the dual-cycle cooling system, the outlet temperature is significantly lowered by 12 °C. Therefore, the hydraulic oil working life and working efficiency in the new cooling system is higher than that in the traditional cooling system. Because the hydraulic oil radiator in the conventional cooling system is air-cooled, its heat dissipation efficiency is lower than that of the liquid-cooled radiator, and the inlet and outlet temperatures of the hydraulic oil radiator in the conventional cooling system fluctuate with the working cycle.

Temperature of hydraulic oil temperature.

As is shown in Fig. 9, the inlet and outlet temperature of the transmission oil within 55 min are collected from the heat exchangers in the traditional cooling system (TC) and the dual-cycle cooling system (DC). If the temperature of the transmission oil is too high, the viscosity will decrease and its transmission efficiency will be affected. Meanwhile, when the equipment is under the condition of continuous high temperature, the wear of parts will be more severe, which will affect the reliability and service life of the loader. Compared with the traditional cooling system, the temperature of the inlet and outlet of the transmission oil heat exchanger of the dual-cycle cooling system is significantly different. Compared with the traditional cooling system, the inlet transmission oil temperature of new cooling system is lowered by 20 °C, and the outlet temperature is reduced by 17 °C.

Temperature of transmission oil temperature.

Three fuel consumption tests were performed on the conventional cooling system and dual-cycle cooling system respectively, and the energy consumption comparison is shown in Table 6. The dual-cycle cooling system consumes less fuel per hour than conventional cooling systems and saves 1% of fuel per hour. The experimental results confirmed that the engine using the dual-cycle cooling system is superior in terms of energy saving and emission reduction.

There are different evaluation criteria for cooling system performance, but they all meet the requirements of heat transfer of various heat sources while trying to meet the following requirements: (1) economical and reasonable; (2) easy to install, clean and repair; (3) the strength is sufficient and the volume is small. From the above analysis, it can be seen that the dual-cycle cooling system has better heat transfer performance than the traditional cooling system. Although the dual-cycle cooling system costs more in terms of manufacturing cost, it is lower than the traditional cooling system in terms of fuel consumption. From the perspective of long-term use of the loader, the economy is better. In order to point out the differences between the two cooling systems in terms of heat transfer performance and volume, the evaluation criteria proposed in this paper are defined as volume coefficient V and effective resistance coefficient P of the cooling system, as shown in the following formula:

where: Vc is the volume of cooling system; ΔPe is the rated power consumption of the cooling system; ΔPr is the pressure drop of the heat dissipation module; ΔP is the pressure drop of the power cabin.

According to the above equation, the performance parameters of the traditional cooling system and the double-cycle cooling system are solved, as shown in Table 7. The air-cooling part of the traditional cooling system has three layers, while the air-cooling part of the double circulation cooling system has only two layers, so the volume coefficient of the double circulation system is increased by 22.9% compared with the traditional system. Similarly, the two-layer structure arrangement reduces the uneven heat dissipation caused by the air backflow between the two layers of radiators, makes the air pressure drop flowing through the radiator lower, improves the utilization rate of cold air, and the effective resistance coefficient of the double-cycle cooling system increases by 7.2%. In summary, the dual-cycle cooling system adopts a water-cooled way to cool down one by one, and the use of coolant improves the heat transfer efficiency of the cooling system.

With the increasing demand for heat dissipation of engineering vehicles, a dual-cycle cooling system is introduced in this paper to prevent the adverse effects of engineering vehicles' equipment when working at the overheating temperature. The performance of the new system is analyzed through tests, and the results show that the dual-cycle cooling system can meet the thermal balance requirements of the engineering vehicle during the shovel operation. Compared with the traditional cooling system, the new cooling system has improved performance in terms of volume, engine energy consumption and oil efficiency. the oil consumption of a wheel loader using the dual-cycle cooling system is reduced by 1% per hour, and the temperature of its transmission oil and hydraulic oil is reduced by more than 10 °C. The new cooling system has bright future in energy saving and emission reduction of engineering vehicles.

The datasets generated and/or analysed during the current study are not publicly available due large volume of data but are available from the corresponding author on reasonable request.

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Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, 130033, China

Chao Yu, Wenbao Zhang, Guangyi Wang, Mian Huang & Jun Sui

32200 Troops of the Chinese People’s Liberation Army, Beijing, China

Huimin Zhao

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Y.C. and Z.W. wrote the main manuscript text. W.G. and H.M. prepared figures. H.Z. has revised the article. All authors reviewed the manuscript.

Correspondence to Wenbao Zhang.

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Yu, C., Zhang, W., Wang, G. et al. Experimental study of dual-cycle thermal management system for engineering radiator. Sci Rep 14, 19691 (2024). https://doi.org/10.1038/s41598-024-70882-w

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Received: 10 April 2024

Accepted: 22 August 2024

Published: 24 August 2024

DOI: https://doi.org/10.1038/s41598-024-70882-w

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