CFD-based Design of Multi-tube Heat Exchange Type Compact Reactor

The production capacity of compact reactors with micrometer or millimeter-scale channels or tubes is increased by numbering-up. In previous studies, a multi-channel plate type reactor and a multi-tube type reactor (MTR) were developed and applied to extraction and reaction operations. Fluid distribution has often been evaluated to design these reactors, but temperature control, which is critical to the reaction, has not been fully considered. It is important to solve this problem and establish a design method. In this study, computational fluid dynamics (CFD)-based design was performed so as to achieve the uniform flow and temperature distributions among the reaction tubes in the MTR, where an exothermic reaction proceeds in each tube with an immobilized catalyst and the reaction temperature is controlled by a coolant flowing outside the tubes. Effects of multi-tube arrangement of lattice, concentric circles and single circle, shell cross-sectional shape of circle, rectangle and ring, and reaction tubes with or without catalyst-free inert sections on the reactor performance were investigated by CFD. The usefulness of a two-step approach of designing the MTR after designing the double-tubular reactor was confirmed through a case study on parallel reactions

Skull metastasis from hepatocellular carcinoma with chronic hepatitis B

A 56-year-old male visited our hospital for evaluation of an occipital mass. Contrast computed tomography showed hypervascular enhancement with osteolytic change in the skull and a huge enhanced mass in the liver. Magnetic resonance imaging showed bone metastasis in the thoracic vertebrae. Assays for hepatitis B surface antigen and hepatitis B core antibody were positive and his liver condition was Child-Pugh grade A. Our diagnosis was hepatocellular carcinoma (HCC) with skull and vertebrae metastases on chronic hepatitis B. He was treated with radiation therapy for bone metastases and transcatheter arterial chemoembolization for HCC. But he developed acute respiratory failure because of aspiration pneumonia, congestion and oedema with haemorrhage of the lungs and died. Dissection showed HCC with multiple bone metastases. The liver tumor was categorized as well-differentiated HCC, Edmondson classification I, trabecular type and pseudoglandular type. In the liver mild infiltration of lymphocytes was seen in Glisson’s capsules which were significantly enlarged with well preserved limiting plates. Piecemeal necrosis was not obvious. No fibrosis was noted. An 8 cm × 7 cm × 3 cm metastatic lesion had formed in the left occipitotemporal part of the cranial bone. The lesion was osteolytic and showed invasion into the dura mater. Neither the subdural cavity nor the brain showed involvement from the metastatic tumor. However, skull metastasis from HCC is very rare and it affects the patient’s prognosis and the quality of life. Therefore, it is very important to make an early diagnosis and carry out proper management of skull metastasis from HCC