## 3 Methods
### Cleaning Phase  
Due to the extensive usage of the units over a long period of time, there is an accumulation of dirt and biological matter that accumulates on various parts of the AC unit, and thus cleaning of the parts of the unit is imperative. The following is a description of the cleaning process. AC parts during the cleaning process go through consecutive steps to reach the desired cleanliness level, as shown in Figure 4. During the cleaning process, AC parts are put on a conveyor and are then moved to the various cleaning sections. In the first phase, all parts are cleaned by compressed air at high pressure (7 bar) to remove the accumulation of dust and solid matter. The second phase is the cleaning of parts with hot steam wherein steam is blasted on the parts to clean them. Finally, all parts are dried using compressed air, so that they are ready for the next step. Figure 4: The processes of the cleaning phase. Figure 3: The disassembly phase modeling using GaBi software. Cleaning involves the use of electricity, desalinated water, and natural gas as a source for heating the water and producing steam. The output is mainly the cleaned parts ready for testing and reassembly. Steam cleaning produces waste water that can be directly connected to the municipal sewage system for further treatment. The design parameters and assumptions of this stage involve, as mentioned earlier, the cleaning process. This is executed on each separate part of the remanufactured AC. The following provides the details of each stage of the cleaning process, along with the assumptions regarding each single stage. Compressed air cleaning:  
In this stage, the parts are cleaned with compressed air that flows at a relatively high speed to clean off residual dust or sand. In order to have the optimum cleaning in this case, the following elements must be incorporated:  
* The air is compressed to 7 bar;
* The pipe used has a diameter of 10 mm;
* Air flow is 4.2 m/s (recommended optimum speed);
* Flow rate is calculated through Q = (60 \(\times\)\(\pi\)\(\times\) d2 \(\times\) V)/4 = 0.1387 Nominal m\({}^{3}\)/s. * Energy consumption is calculated (0.059 MJ) based on the energy consumption of the selected air compressor. Steam cleaning:  
In this stage, the parts are washed using steam to remove any residual dirt and mud. The process design parameters and assumptions are as follows:  
* A pump of a power rating of 7.5 KW and provides a flow rate of 1000 L/h is used;
* Parts of each AC unit require 5 min cleaning with steam;
* Power consumption is 0.625 KW per cleaned part. Compressed air drying:  
After the units pass through steam cleaning. they are dried using compressed air. The assumptions in this case are similar to that in the first step (i.e., compressed air cleaning), except for the amount of air and energy, in this case, they are doubled to 0.118 MJ and 0.277 Nm\({}^{3}\) respectively. Material handling:  
In order to move each part from one place to another, the conveyor is used for this purpose. It is assumed to be motorized, thus satisfying the mass production demand. The assumptions for the material handling throughout the processes are listed below:  
* The cleaning stages are separated by a distance of 5 m;
* The four conveyors used are 5 m long;
* The conveyors are run on a 1 hp motor and provide a speed of 0.2032 m/s for each unit;
* Energy consumption is calculated (0.07345 MJ). The total life cycle inventory of this phase comes from the process's individual LCI, which are:  
1. LCI related to natural gas consumption in steam generation;
2. LCI related to electricity for compressed air;
3. LCI related to electricity for material handling conveyor;
4. LCI related to water desalination;
5. LCI related to waste water treatment. As the steam generation process, electricity generation, and water desalination are assumed to use natural gas as a source of energy, the input and output of these processes will be the same.