This design is roughly based on a real Victorian cast-iron design, except that it has a number of enhancements and features. These are:- Classic open fire design, for burning coal, wood or man-made fuels- Side convection heat pipes circulate clean air from the room past the main heat source and back into the room. This increases the heat transfer from the burning fuel into the room- Rear water pipes for opportunistic water heating when the fire is burning. Most likely used with a heat-store system, or as-and-when central heating systems- Forward shifted grate to bring the radiant heat closer to the room and to enourage greater heat transfer outwards rather than up the chimney- Upwards heat and smoke is diverted by the fireplace, meaning heat is transferred to it, again transferring more heat to the room and less to the chimney- Places to add decorative tiles or patterns (again, like many Victorian fireplaces)All open fires are inherently inefficient (in terms of the energy of the fuel and the energy transferred to the room). The up-draft of heat up the chimney also tends to "suck" the air (and heat) out of the room and wastes it up the chimney. However, this open-fire design aims to increase the amount of "usable" heat from the burning fuel. It's probably not as good as a wood burning stove, but hopefully a lot better than an original Victorian fireplace.Just about all of the sizes, scales and tolerances are very forgiving. The Sketchup source file is included to make derivatives. The object is around 100mm square, so obviously needs scaling to make a model or for using as a building template.