water jacket
water-filled casing surrounding a device, typically a metal sheath having intake and outlet vents to allow water to be pumped through and circulated
en-US/ˈwɔtɚ ˈd͡ʒækət/
en-GB/ˈwɔːtə ˈd͡ʒækɪt/
water-filled casing surrounding a device, typically a metal sheath having intake and outlet vents to allow water to be pumped through and circulated