Material selection and optimisation of a high-temper[at]ure compact heat exchanger
Abstract
The Pebble Bed Micro Model (PBMM) plant currently employs a large conventional
shell-and-tube heat exchanger as recuperator at the inlet to the heat source in order to preheat
the nitrogen. The thermal inertia of the current PBMM recuperator influences the
dynamic behaviour of the plant and the heat exchanger configuration is also different
from the actual Pebble Bed Modular Reactor (PBMR) plant, which will employ a
compact heat exchanger.
A need therefore exists to design a high-temperature compact heat exchanger for the
PBMM plant. This study includes the material selection and optimization of the
proposed heat exchanger design.
The material chosen for this recuperator is a tungsten-copper alloy with 68 wt% W and
32 wt% Cu. A mini-channel heat exchanger with a counter flow configuration is the
chosen type of heat exchanger. The heat exchanger is made up of two types of plates that
are stacked alternatively. These plates are then either diffusion bonded or brazed in order
to form the complete heat exchanger.
The final geometry of the recuperator is as follows:
- Total length -- 0.75 m
- Total width -- 0.518 m
- Total height -- 0.8 m
- Number of channels wide -- 370
- Number of hot channels high -- 200
- Number of cold channels high -- 200
- Plate thickness - 1 mm
- Fin thickness -- 0.4 mm
- Channel height -- 1 mm
- Channel width - 1 mm
The proposed recuperator only occupies 10% of the footprint area and 13% of the volume
of the shell-and-tube recuperator. Its affectivity is 95%, which results in an increase of
2% in the cycle affectivity. The response time for the compact recuperator is about 25%
that of the shell-and-tube recuperator.
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- Engineering [1379]