# Dynamic Performance Analysis for an Absorption Chiller under Different Working Conditions
## 5 Application Analysis  
To further clarify the application of the models, a whole system is built up. The AC is applied in a process plant used for raw material storage, whose temperature must be lower than 21 \({}^{\circ}\)C, otherwise the raw materials can decompose. The plant cooling load is simply calculated by:  
\[Q_{load}=UA_{load}\cdot(T_{out}-T_{in}) \tag{34}\]  
where \(UA_{load}\) is the product of the heat transfer coefficient and heat transfer area of the process plant, and is set as 0.3697 kW/K; \(T_{out}\) is the outdoor air temperature, \({}^{\circ}\)C; and \(T_{in}\) is the indoor temperature, \({}^{\circ}\)C.  
And there is also thermal storage for the process plant:  
\[Q_{load}-Q_{e,ext}=MCp_{load}\cdot\frac{dT_{in}}{dt} \tag{35}\]  
where \(MCp_{load}\) is the thermal capacity of the process plant, which is set to be 10 kJ/K. The outdoor temperature is 35 \({}^{\circ}\)C. The indoor temperature is 20 \({}^{\circ}\)C at the beginning, and the plant cooling load is 5.55 kW, but there will be some raw materials entering the process plant at a known time, which is expected to make the cooling load 1.4 kW higher. To meet the increased cooling demand, the AC cooling capacity is supposed to be increased accordingly. Based on Figure 7, the generator inlet temperature can grow from 90 \({}^{\circ}\)C to 100 \({}^{\circ}\)C when the cooling water inlet temperature \(T_{cin}\) and the evaporator inlet temperature \(T_{cin}\) are 32 \({}^{\circ}\)C and 12 \({}^{\circ}\)C, respectively. In this study, two control methods are calculated, and the variations of the AC cooling capacity, indoor temperature and the plant cooling load are displayed in Figure 13a,b. Figure 13a is adjusting the AC when the raw materials enter the process plant at time 0. The cooling load steeply becomes higher than the AC cooling capacity, which grows slowly, so the indoor temperature increases as high as 22.3 \({}^{\circ}\)C. Meanwhile, the outdoor temperature does not change, thus the cooling load reduces gradually. When the cooling load is lower than the AC cooling capacity, the indoor temperature starts to decrease, and the cooling load rises again until it equals to the AC cooling capacity. Finally, the indoor temperature reaches a new steady-state around 20 \({}^{\circ}\)C.  
Variations of the AC cooling capacity, the indoor temperature and the plant cooling load are displayed in Figure 13b when the AC is adjusted 366 s earlier before these raw materials arrive, and this is the relaxation time according to Figure 8. The AC cooling capacity is higher than the plant cooling load after time 0, so the indoor temperature decreases, leading to the rise of the cooling load. When the time is 366 s, the cooling load has a 1.4 kW step change due to the new coming raw materials,  
Figure 12: The effect of different \(T_{cin}\) on the relaxation time and \(\Delta Q_{e}\). as a consequence, the indoor temperature increases to near 20 \({}^{\circ}\)C, and then the plant cooling load decreases gradually until it becomes the same as the AC cooling capacity. In this dynamic process, the indoor temperature is always lower than 21 \({}^{\circ}\)C.  
If the AC starts to be adjusted when the plant cooling load has a change, the indoor temperature can be higher than 21 \({}^{\circ}\)C in Figure 13a, while the indoor temperature cannot exceed the upper limit with early adjustment of AC. And in Figure 13b, the time starting to adjust can refer to the results in Part 4 when the working conditions are different. For example, the AC can start to change 354 s earlier when \(T_{cin}\) = 25 \({}^{\circ}\)C and \(T_{ein}\) = 12 \({}^{\circ}\)C. These two control methods may be too simple, however, they demonstrate that the dynamic performance is beneficial for the adjustment of AC and the control of the whole system, which the AC belongs to. Thus, the AC transient process should be considered when the control strategy is made in the real practices.