Pressure vessel

A pressure vessel comprising

• a pressure vessel body having a rectangular cross-sectional shape and formed to extend in a longitudinal direction,
• wherein the pressure vessel body includes
• a first flow channel which is formed in the longitudinal direction of the pressure vessel body and through which a first fluid is capable of flowing,
• a second flow channel which is formed in the longitudinal direction of the pressure vessel body and through which a second fluid is capable of flowing,
• a first-fluid inlet-outlet port which is provided in one longitudinal end surface of the pressure vessel body and connects with the first flow channel and through which the first fluid is capable of flowing in or out,
• a second-fluid inlet-outlet port which is provided in another longitudinal end surface of the pressure vessel body and connects with the second flow channel and through which the second fluid is capable of flowing in or out,
• an opening portion which is formed by opening a portion of one end surface which is the same as the one longitudinal end surface of the pressure vessel body provided with the first-fluid inlet-outlet port and connects with the second flow channel,
• a closing member which is inserted and fitted into the opening portion and made of stainless steel, a Ni alloy, or a ceramic to close the opening portion in a demountable manner,
• a first lid member which is provided at the one longitudinal end surface of the pressure vessel body provided with the first-fluid inlet-outlet port and the opening portion, and has an opening and closing structure, and
• a second lid member which is provided at the another longitudinal end surface of the pressure vessel body provided with the second-fluid inlet-outlet port, and has no opening and closing structure.