A valve, comprising: a housing defining an interior and including a valve seat and a structure fixedly disposed remote from the valve seat; a valve head to open and close the valve seat, fluid being permitted to flow into the interior when the valve seat is open; and an elastic system anchored on the structure and coupled to the valve head, the elastic system including a biasing element and an elastic element formed of memory metal alloy disposed to contact fluid permitted to flow into the interior, wherein the biasing element and the elastic element are configured to cooperatively move the valve head toward one of a valve seat open position and a valve seat closed position, preferably a valve seat open position, when the fluid temperature is below a lower limit, such that motion of the valve head in one direction begins at a first temperature and that the valve head reaches its full displacement at a second temperature; and the biasing element and the elastic element are configured to cooperatively move the valve head toward the other of a valve seat open position and a valve seat closed position, preferably a valve seat closed position, when the fluid temperature is above an upper limit, such that motion of the valve head in an opposite direction begins at a third temperature and that the valve head reaches its original non-displaced position at a fourth temperature; characterized in that the valve further comprises a pressure relief element anchored on the structure and interposed between the structure and the elastic element, the elastic element being preferably interposed between the pressure relief element and the biasing element. a housing defining an interior and including a valve seat and a structure fixedly disposed remote from the valve seat; a valve head to open and close the valve seat, fluid being permitted to flow into the interior when the valve seat is open; and an elastic system anchored on the structure and coupled to the valve head, the elastic system including a biasing element and an elastic element formed of memory metal alloy disposed to contact fluid permitted to flow into the interior, wherein the biasing element and the elastic element are configured to cooperatively move the valve head toward one of a valve seat open position and a valve seat closed position, preferably a valve seat open position, when the fluid temperature is below a lower limit, such that motion of the valve head in one direction begins at a first temperature and that the valve head reaches its full displacement at a second temperature; and the biasing element and the elastic element are configured to cooperatively move the valve head toward the other of a valve seat open position and a valve seat closed position, preferably a valve seat closed position, when the fluid temperature is above an upper limit, such that motion of the valve head in an opposite direction begins at a third temperature and that the valve head reaches its original non-displaced position at a fourth temperature; characterized in that the valve further comprises a pressure relief element anchored on the structure and interposed between the structure and the elastic element, the elastic element being preferably interposed between the pressure relief element and the biasing element.