fix spelling, grammar, formatting

[mefuller]

As mentioned in #59 , additional information defining the meaning of h, U and Q and their units for heat transfer models must be added tot he documentation.

[codecov]

Codecov Report

Merging #60 (3e5d58d) into main (ce44838) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #60   +/-   ##
=======================================
  Coverage   94.74%   94.74%           
=======================================
  Files           6        6           
  Lines         819      819           
=======================================
  Hits          776      776           
  Misses         43       43           

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