*5.3. Total Heating Capacity of Integrated System with Serial and Parallel Circuits*

The total heating capacities comparison of the integrated system with serial and parallel circuits for various heater powers is presented in Figure 7. In addition, in the case of an integrated system with parallel circuit, the effect of flow ratio on total heating capacity is also included. As presented in Figure 7, the total heating capacity for parallel circuit is the sum of heating capacities of battery and HVAC at all heater powers and flow ratios, whereas the total heating capacity for the serial circuit is the heating capacity of the battery when the battery only heated using an entire flow rate, and that is the heating capacity of HVAC when only HVAC is heated using a full flow rate of working fluid. In the integrated system with parallel circuit, the total flow rate of working fluid (24 L/min) is divided to heat up the battery and HVAC therefore, the total heating capacity is the sum of heating capacities of battery and HVAC. While, in the case of an integrated system with serial circuit, the total flow rate of working fluid is used for heating of battery or heating of HVAC, therefore, the heating capacity of the battery or heating capacity of HVAC is only the total heating capacity. In total, the heating capacity of the integrated system with parallel circuit, the heating capacity of HVAC is more dominant compare with heating capacity of battery. Therefore, the total heating capacity of the integrated system with parallel circuit decreases as the flow ratio increases for all heater powers because of decrease in the heating capacity of HVAC. The maximum total heating capacities for the integrated system with parallel circuit are found at flow ratio of 2/8 for heater powers of 2 kW, 4 kW and 6 kW, which are 1439.66 W, 2139.60 W and 3938.59 W, respectively. For the integrated system with serial and parallel circuits, the total heating capacity increases as the heater power increases. The total heating capacity increases by 173.50% for the integrated system with parallel circuit, 204.80% for battery heating of integrated system with serial circuit and 197% for HVAC heating of the integrated system with serial circuit, as the heater power increases from 2 kW to 6 kW. For heater power of 2 kW, the maximum total heating capacity of the integrated system with parallel circuit is 327.90% higher than total battery heating capacity of the integrated system with serial circuit, and that is 25.30% lower than total HVAC heating capacity of the integrated system serial circuit. At heater power of 4 kW, the total heating capacity of the integrated system with parallel circuit is 212.30% higher and 42.30% lower than the total battery heating capacity and total HVAC heating capacity of the integrated system with serial circuit, respectively. In the same way, at a heater power of 6 kW, the total heating capacity of integrated system with parallel circuit is 284.20% higher and 31.20% lower than the total battery heating capacity and total HVAC heating capacity of the integrated system with serial circuit, respectively. As shown in Figure 7, the output as the sum of heating capacities of battery and HVAC in the case of parallel circuit and heating capacity of battery or HVAC in the case of serial circuit are lower than the input as heater power. The heat losses for the integrated system with serial and parallel circuits are occurred into experimental components. as well as three valves, pipes and pipe fittings/connections. In addition, some heat loss occurs from working fluid to ambient. The integrated system with serial circuit shows rapid heating performance compared with the integrated system with parallel circuit, but the tradeoff heating between battery and HVAC is not possible in the case of the integrated system with serial circuit. However, the integrated system with parallel circuit enables the tradeoff between the heating of HVAC and that of the battery. Despite of slow heating performance of the integrated system with parallel circuit, the desired heating performance could be achieved.

**Figure 7.** Comparison of total heating capacities of parallel and serial circuits for various heater powers. **Figure 7.** Comparison of total heating capacities of parallel and serial circuits for various heater powers.

#### *5.4. ANN Model for Battery and HVAC Heating Performances 5.4. ANN Model for Battery and HVAC Heating Performances*

The battery and HVAC heating performances of the integrated system with serial and parallel circuits predicted by ANN model with various algorithm are compared with corresponding experimental (actual) results. The comparison of predicted results and actual results is done in terms of three statistical parameters namely, coefficient of determination (R2), root mean square error (RMSE) and coefficient of variance (COV). The algorithm with highest value of R2 and lowest values of RMSE and COV are suggested as the optimum algorithm for ANN model. The battery and HVAC heating performances of the integrated system with serial and parallel circuits predicted by ANN model with various algorithm are compared with corresponding experimental (actual) results. The comparison of predicted results and actual results is done in terms of three statistical parameters namely, coefficient of determination (R<sup>2</sup> ), root mean square error (RMSE) and coefficient of variance (COV). The algorithm with highest value of R<sup>2</sup> and lowest values of RMSE and COV are suggested as the optimum algorithm for ANN model.
