Inner spiral grooved tube with excellent heat transfer property and heat exchanger

An inner spiral grooved tube, comprising:

• a tube body;
• and
• a plurality of grooves and a plurality of fins aligned in an inner circumferential direction of the tube body, wherein
• the grooves and the fins are formed in a spiral along a longitudinal direction of the tube body,
• an outer diameter of the tube body is 3 mm or more and 10 mm or less,
• a number of the fins formed on an inner peripheral surface of the tube body is 30 to 60,
• the inner spiral grooved tube is made of a metal,
• a cross sectional shape of each of the fins in a cross section of the tube body has an isopod trapezoidal shape, an apex angle formed by sidewalls of the isopod trapezoidal shape being −2.5° or more and 2.5° or less,
• a ratio h/f is 1.750 or more and 3.161 or less, h being a fin height and f being fin width,
• a ratio c/f is 1.547 or more and 2.965 or less, c being a fin spacing between adjacent fins in the inner circumferential direction of the tube body,
• an average obtained by summing the ratio h/f and the ratio c/f and dividing a sum in half is 2.4 or more and 2.6 or less,
• the fins are arranged with an equal spacing in the inner circumferential direction of the tube body,
• the tube body is made of aluminum or an aluminum alloy,
• an average of the upper width and the lower width of the fin is 0.091 mm or more and 0.138 or less, and
• the fin height is 0.227 mm or more and 0.392 mm or less.