Er...

Excerpts from Weiyang's thermodynamics lab report:

Volume flow rate for hot water, q_vh = 3 litre/minute = 5×10^-5m³/s
Volume flow rate for cold water, q_vc = 2 litre/minute = 3.33×10^-5m³/s

Density of Water = 1000kg/m³
Density of Water at 60°C = 983kg/m³

Mass flow rate for hot water, q_mh = 5×10^-5×983 = 0.04915kg/s
Mass flow rate for cold water, q_mc = 3.33×10^-5×1000 = 0.0333kg/s

Heat power emitted from hot fluid, Q_e = q_mh(C_p)_h(T₁-T₂)
= 0.04915×4.18×(60.0-64.8)
= –0.98615W

Heat power absorbed by cold fluid, Q_a = q_mc(C_p)_c(T₄-T₃)
= 0.0333×4.18×(34.7-27.4)
= 1.01612W

Heat power lost, Q_f = 0.98615 – 1.01612 = -0.2997W

Overall efficiency, η = 1.01612/0.98615 × 100% = 103.04%

...which means my lab group members should win the Nobel Prize. Oh well, either that or there's something wrong with the experiment machine and the experimenters.