Abstract: A tubular reactor which acts as a combustor and heat exchanger is disclosed. Such reactor supplants a system with a combustor having a heat exchanger arranged around the combustor. The combined system includes a diffuser having an inlet for a fuel-and-air mixture and a plurality of holes defined in its surface through which the fuel-and-air mixture exits the diffuser and a plurality of tubes. First linear portions along the length of each tube are mutually parallel with a centerline of the first portions of the tubes displaced from the diffuser by a predetermined distance. Centerlines of the linear portions of adjacent tubes are displaced from each other by a predetermined gap. The fuel and air combust in the proximity of the first portion of the tubes for effective heat transfer to gases traveling through the tubes. Such a tubular reactor can be employed within a thermal-compression heat pump.