Abstract: An apparatus for cooling at least two heated surfaces includes a base plate defining multiple upper and lower supply manifolds and upper and lower exhaust manifolds. The upper and lower supply (exhaust) manifolds receive (exhaust) coolant, and the upper (lower) supply and exhaust manifolds are interleaved. The apparatus further includes an upper substrate having an inner surface and an outer surface. The inner surface is coupled to the base plate and defines multiple microchannels for receiving and exhausting coolant. The outer surface is in thermal contact with one of the heated surfaces. The apparatus further includes a lower substrate having an inner surface and an outer surface. The inner surface is coupled to the base plate and defines multiple microchannels for receiving and delivering coolant. The outer surface is in thermal contact with another of the heated surfaces. The apparatus further includes a supply plenum and an exhaust plenum oriented in a plane of the base plate.

Abstract: A method for measuring a lower heating value of a gaseous fuel. The method includes mixing a gaseous fuel with air to provide a combustible air-fuel mixture. The air-fuel mixture is directed to flow across a flow surface of a first micro-hotplate maintained at a constant temperature. A change in power required to maintain a constant temperature of the first micro-hotplate flow surface due to a convective and conductive heat transfer from the first micro-hotplate flow surface to the air-fuel mixture is measured. The air-fuel mixture is directed to flow across a flow surface of a second micro-hotplate maintained at a constant temperature. The air-fuel mixture is combusted as the air-fuel mixture flows across the second micro-hotplate flow surface. A change in power required to maintain a constant temperature of the second micro-hotplate flow surface due to the combustion of the air-fuel mixture is measured.

Abstract: An apparatus for cooling at least one heated surface includes a base plate defining a number of inlet and outlet manifolds. The inlet manifolds are configured to receive a coolant, and the outlet manifolds exhaust the coolant. The inlet and outlet manifolds are interleaved. The apparatus also includes at least one substrate having inner and outer surfaces. The inner surface is coupled to the base plate and defines a number of microchannels that receive the coolant from the inlet manifolds and deliver the coolant to the outlet manifolds. The microchannels are oriented substantially perpendicular to the inlet and outlet manifolds. The outer surface is in thermal contact with the heated surface. The apparatus also includes an inlet plenum that supplies the coolant to the inlet manifolds, and an outlet plenum that exhausts the coolant from the outlet manifolds. The inlet plenum and outlet plenum are oriented in a plane of the base plate.