A heat transfer device for enclosing a heat source and facilitating convective heat transfer from the heat source, comprising: an outer wall having an outer surface exposed to an environment of the heat transfer device and defining an outer shape of the heat transfer device; and an inner wall defining a flow passage through the heat transfer device, wherein the outer wall and the inner wall collectively define an internal volume that is configured to house or otherwise affix to the heat source, and wherein the flow passage comprises: an inlet configured to receive a fluid from the environment; an outlet configured to exhaust the fluid from the flow passage; a core region extending between the inlet and the outlet and configured to deliver the fluid from the inlet to the outlet and allow heat to exchange between the fluid within the core region and the internal volume; and heat transfer structures extending inwardly from the inner wall into the core region, and wherein the heat transfer structures are configured to facilitate heat exchange between the heat source and the fluid in the core region, wherein the inlet comprises an outer opening that is adjacent to the outer wall and an inner opening that is adjacent to the core region, and wherein a diameter of the outer opening is greater than a diameter of the inner opening, the outer opening of the inlet adjoining the outer wall; and wherein at least one of a portion of the inner wall that defines the core region and the heat transfer structures is configured to cause the fluid in the core region to twist around a longitudinal axis of the flow passage as the fluid flows from the inlet to the outlet. an outer wall having an outer surface exposed to an environment of the heat transfer device and defining an outer shape of the heat transfer device; and an inner wall defining a flow passage through the heat transfer device, wherein the outer wall and the inner wall collectively define an internal volume that is configured to house or otherwise affix to the heat source, and wherein the flow passage comprises: an inlet configured to receive a fluid from the environment; an outlet configured to exhaust the fluid from the flow passage; a core region extending between the inlet and the outlet and configured to deliver the fluid from the inlet to the outlet and allow heat to exchange between the fluid within the core region and the internal volume; and heat transfer structures extending inwardly from the inner wall into the core region, and wherein the heat transfer structures are configured to facilitate heat exchange between the heat source and the fluid in the core region, wherein the inlet comprises an outer opening that is adjacent to the outer wall and an inner opening that is adjacent to the core region, and wherein a diameter of the outer opening is greater than a diameter of the inner opening, the outer opening of the inlet adjoining the outer wall; and wherein at least one of a portion of the inner wall that defines the core region and the heat transfer structures is configured to cause the fluid in the core region to twist around a longitudinal axis of the flow passage as the fluid flows from the inlet to the outlet. an inlet configured to receive a fluid from the environment; an outlet configured to exhaust the fluid from the flow passage; a core region extending between the inlet and the outlet and configured to deliver the fluid from the inlet to the outlet and allow heat to exchange between the fluid within the core region and the internal volume; and heat transfer structures extending inwardly from the inner wall into the core region, and wherein the heat transfer structures are configured to facilitate heat exchange between the heat source and the fluid in the core region, wherein the inlet comprises an outer opening that is adjacent to the outer wall and an inner opening that is adjacent to the core region, and wherein a diameter of the outer opening is greater than a diameter of the inner opening, the outer opening of the inlet adjoining the outer wall; and wherein at least one of a portion of the inner wall that defines the core region and the heat transfer structures is configured to cause the fluid in the core region to twist around a longitudinal axis of the flow passage as the fluid flows from the inlet to the outlet.