Abstract: A wearable heater and/or cooler device can include one or more fluid pumps, one or more conduits, and one or more chambers. The fluid pumps can be configured for generating flow of a fluid and comprise inlets and outlets. The conduits have first end portions and second end portions, and the first end portions of the conduits can be coupled to the outlets of the fluid pumps. The chambers can be coupled to second end portions of the conduits such that the fluid flows from the fluid pumps, through the conduits, and into the chambers. The chambers can be configured to enhance the desired thermal transport characteristics of the fluid for thermal transfer adjacent to a wearer's body.