“…Out of total twenty nine research papers, ten research papers [2][3][4][5][6][7][8][9][10][11] are related to double pipe heat exchanger, six research papers [12][13][14][15][16][17] are in the field of shell and tube heat exchanger, twelve studies [18][19][20][21][22][23][24][25][26][27][28][29] are in other type of heat exchangers and one [30] in the field of phase change material. Nine researchers [2-6, 13, 16, 25, 26] have utilized Al2O3 based nanofluid, three [7,8,10] have employed TiO2 based nanofluid, while two -two studies are carried out using CuO2 [24,30], MWCNT [14,22] and Fe2O3 [9,20] based nanofluids.…”