SDCS Regenerator Component Analysis

This section presents the results and analysis from the regenerator component investigation. The analysis investigates the impact changes in environmental and operating conditions have on the performance of the regenerator. The variables considered are inlet air temperature, inlet air relative humidity, air volumetric flow and desiccant solution volumetric flow. Two further tests, aiming to consider the impact of the SOFC CHP system operation on regenerator performance are also conducted. These are hot water flow temperature and hot water volumetric flow in the heating circuit. The regenerator variables investigated have been selected because they impact regenerator performance, but are also dictated by the SOFC CHP system performance. Optimisation of both sets of variables will facilitate effective pairing of the two systems during tri-generation system integration. Unless otherwise varied, Table 6.2 lists the constants used in the regenerator investigation.

The base condition for the inlet air to the regenerator is that of ‘room’ air. As discussed in Chaps. 3 and 4, a lower temperature and relative humidity will improve regenerator performance. During the regenerator tests, the hot water flow temperature and hot water volumetric flow range used is 45-60 °C and 0.53.5 L min-1 respectively. The thermal input values used in the regenerator evaluation are based upon those typical of a SOFC CHP system found in the literature, such as the BlueGEN unit presented in Chap. 7. This assumption aims to simulate the SDCS operation in a SOFC tri-generation system application, and thus facilitate successful tri-generation system integration in Chap. 7.

The key regenerator performance metrics considered in this section are: moisture addition rate, latent (regenerator) effectiveness and regenerator thermal input. The regenerator thermal input has been measured on the hot water heating side

Table 6.2 Regenerator operational constants

Variable

Value

Inlet air temperature (°C)

26

Inlet air relative humidity (%)

60

Air volumetric flow (m3 h-1)

256

Desiccant solution volumetric flow (L min-1)

3.2

Desiccant solution mass concentration (-)

0.650.7

Regenerator water volumetric flow (L min-1)

2

Regenerator water flow temperature (°C)

55

Steady state performance of the SDCS regenerator over a 1 h period a moisture addition rate and, b regenerator psychrometiic process

Fig. 6.9 Steady state performance of the SDCS regenerator over a 1 h period a moisture addition rate and, b regenerator psychrometiic process

using Eq. 5.4. Where appropriate, the change in water temperature across the regenerator plate heat exchanger (PX2) is also included (Arwater). This is to assist with optimisation of the regeneration process with the SOFC CHP system’s thermal output during tri-generation system integration.

Figure 6.9a presents the performance of the regenerator over a 1 h period, with an average inlet temperature of 27.36 °C and relative humidity of 60.57 %. The average moisture addition rate and latent (regenerator) effectiveness over this period was 0.3527 g s-1 and 34.7 % respectively. The average regenerator thermal input during this period was 1343 W. Figure 6.9b demonstrates the regeneration process on a psychrometric chart. The data is provided to illustrate the steady-state operation of the regenerator during laboratory experimentation. Throughout all tests the regenerator plate heat exchanger (PX2) effectiveness ranged from 60 to 80 %.

 
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