F24VCOLLECTION, PRODUCTION OR USE OF HEAT NOT OTHERWISE PROVIDED FOR F24V30/00 F24V30/00Apparatus or devices using heat produced by exothermal chemical reactions other than combustion F24V40/00Production or use of heat resulting from internal friction of moving fluids or from friction between fluids and moving bodies F24V40/10the fluid passing through restriction means F24V50/00Use of heat from natural sources, e.g. from the sea F24V99/00Subject matter not provided for in other main groups of this subclass