A heat exchanger (1, 2, 4), comprising: a first fluid flow guide (11, 21, 41) having an opening (111, 211, 411), a cavity (113, 212, 441) and a first fluid outlet (112, 213, 413), wherein the opening (111, 211, 411) is used for intake of a first fluid, and the first fluid outlet (112, 213, 413) is for discharging the first fluid; a second fluid flow guide (13, 23, 43) having a second fluid inlet (131, 231, 431), a flow diversion chamber (132, 232, 432), a plurality of heat exchange tubes (133, 233, 433) each defining a fluid flow path, a flow collection chamber (134, 234, 434) and a second fluid outlet (135, 235, 435), the second fluid inlet (131, 231, 431) for intake of a second fluid having a temperature different from that of the first fluid, wherein the flow diversion chamber (132, 232, 432) is arranged to divert a second fluid from the second fluid inlet (131, 231, 431) into the plurality of heat exchange tubes (133, 233, 433), for collection in the flow collection chamber (134, 234, 434) and subsequent discharge from the second fluid outlet, the second fluid flow guide (13, 23, 43) being located in the cavity (113, 212, 441) of the first fluid flow guide (11, 21, 41) to form a plurality of first fluid spaces (141, 251, 437, 438) surrounding the plurality of heat exchange tubes (133, 233, 433), said first fluid spaces being connected with the opening (111, 211, 411) and the first fluid outlet (112, 213, 413) of the first fluid flow guide to guide the first fluid around the plurality of heat exchange tubes (133, 233, 433) from the opening (111, 211, 411) to the first fluid outlet (112, 213, 413), wherein upon flow of the second fluid along the plurality of heat exchange tubes the second fluid undergoes heat exchange with the first fluid flowing through the first fluid spaces so as to change the temperature of the second fluid before the second fluid is subsequently discharged from the second fluid outlet, characterized in that walls of the first fluid spaces and walls of the fluid flow path of each heat exchange tube comprise non-axial flow guide structures for promoting the first fluid and the second fluid to flow in a non-axial direction. a first fluid flow guide (11, 21, 41) having an opening (111, 211, 411), a cavity (113, 212, 441) and a first fluid outlet (112, 213, 413), wherein the opening (111, 211, 411) is used for intake of a first fluid, and the first fluid outlet (112, 213, 413) is for discharging the first fluid; a second fluid flow guide (13, 23, 43) having a second fluid inlet (131, 231, 431), a flow diversion chamber (132, 232, 432), a plurality of heat exchange tubes (133, 233, 433) each defining a fluid flow path, a flow collection chamber (134, 234, 434) and a second fluid outlet (135, 235, 435), the second fluid inlet (131, 231, 431) for intake of a second fluid having a temperature different from that of the first fluid, wherein the flow diversion chamber (132, 232, 432) is arranged to divert a second fluid from the second fluid inlet (131, 231, 431) into the plurality of heat exchange tubes (133, 233, 433), for collection in the flow collection chamber (134, 234, 434) and subsequent discharge from the second fluid outlet, the second fluid flow guide (13, 23, 43) being located in the cavity (113, 212, 441) of the first fluid flow guide (11, 21, 41) to form a plurality of first fluid spaces (141, 251, 437, 438) surrounding the plurality of heat exchange tubes (133, 233, 433), said first fluid spaces being connected with the opening (111, 211, 411) and the first fluid outlet (112, 213, 413) of the first fluid flow guide to guide the first fluid around the plurality of heat exchange tubes (133, 233, 433) from the opening (111, 211, 411) to the first fluid outlet (112, 213, 413), wherein upon flow of the second fluid along the plurality of heat exchange tubes the second fluid undergoes heat exchange with the first fluid flowing through the first fluid spaces so as to change the temperature of the second fluid before the second fluid is subsequently discharged from the second fluid outlet, characterized in that walls of the first fluid spaces and walls of the fluid flow path of each heat exchange tube comprise non-axial flow guide structures for promoting the first fluid and the second fluid to flow in a non-axial direction.