Methods and systems for a heat exchanger

A heat exchanger, comprising:

• a primary fluid path comprising a primary outer shell enclosing a primary cavity through which a primary fluid can flow;
• and
• a secondary fluid path coupled to the primary fluid path and comprising a secondary fluid supply conduit, a secondary fluid exit conduit, and multiple heat transfer elements coupled fluidly between the secondary fluid supply conduit and the secondary fluid exit conduit and disposed in series and adjacent to one another in the primary cavity, wherein the secondary fluid path is configured such that a secondary fluid can flow through the secondary fluid supply conduit, the multiple heat transfer elements, and the secondary fluid exit conduit, which are in fluid communication with one another;
• wherein the multiple heat transfer elements are disposed in the primary cavity such that the primary fluid contacts the multiple heat transfer elements,
• wherein a heat exchange amount resulting from the primary fluid contacting each of the multiple heat transfer elements can be calculated for each of the multiple heat transfer elements, wherein a needed number of the multiple heat transfer elements coupled fluidly between the secondary fluid supply conduit and the secondary fluid exit conduit and disposed in the primary cavity to achieve a desired output temperature for the primary fluid can be determined, and
• wherein the primary outer shell comprises an opening and a hatch disposed within the opening, wherein the hatch is configured to fluidly separate the primary cavity from a surrounding environment external to the primary cavity, wherein the hatch is removable to expose the opening causing the primary cavity to be in fluid communication with the surrounding environment, wherein the hatch and the opening have a size and a shape that are complementary to a size and shape of one or more of the multiple heat transfer elements, wherein the hatch is configured to allow addition or removal of one or more of the multiple heat transfer elements to or from the primary cavity to achieve the desired output temperature.