The thermal masses of components influence the performance of many adsorption heat pump systems. However, typically when experimental adsorption systems are reported, data on thermal mass are missing or incomplete. This work provides original measurements of the thermal masses for experimental sorption heat exchanger hardware. Much of this hardware was previously reported in the literature, but without detailed thermal mass data. The data reported in this work are the first values reported in the literature to thoroughly account for all thermal masses, including heat transfer fluid. The impact of thermal mass on system performance is also discussed, with detailed calculation left for future work. The degree to which heat transfer fluid contributes to overall effective thermal mass is also discussed, with detailed calculation left for future work. This work provides a framework for future reporting of experimental thermal masses. The utilization of this framework will enrich the data available for model validation and provide a more thorough accounting of adsorption heat pumps.
Gas-fired heat pumps are a potential replacement for condensing boilers, utilizing fossil-fuel resources more efficiently and reducing the amount of biogas or hydrogen required in sustainable gas grids. However, their adoption has been limited due to their large size and high capital cost, resulting in long payback times. For adsorption-based heat pumps, the major development challenge is to maximize the rate of heat transfer to the adsorbent, whilst minimizing the thermal mass. This work develops a modular finned-tube carbon–ammonia adsorption generator that incorporates the adsorbent in highly compacted 3-mm layers between aluminum fins. Manufacturing techniques that are amenable to low cost and high-volume production were developed. The module was tested using the large temperature jump (LTJ) method and achieved a time constant for adsorption and desorption of 50 s. The computational model predicted that if incorporated into two adsorption generators of 6 L volume each, they could be used to construct a gas-fired heat pump with a 10 kW heat output and a gas utilization efficiency (GUE, the ratio of useful heat output to higher calorific value of gas used) of 1.2.
The design of an adsorption solar air conditioning system is investigated by using a model with an activated carbon–methanol working pair. This system is analysed with the solar insolation levels and ambient temperatures of Singapore. The proposed design mainly consists of two tubular reactor heat exchangers (TRHEXs) operating out of phase and driven by heat from an evacuated tube solar collector (ETSC). The pair of TRHEXs act as a thermal compressor and contain about 2.275 kg of activated carbon per reactor. The evacuated tube solar collector (ETSC) has better performance and is more cost effective than the flat plate solar collector (FPSC), even though it has a higher cost per unit. On the hottest day of the year, the proposed adsorption system has a maximum cooling power of 2.6 kW and a COP of 0.43 at a maximum driving temperature of 139 °C with a 9.8 m2 ETSC area. The system has a total estimated cost of EUR 10,550 corresponding to about SGD 14,800 with a 7-year payback time. At similar cooling capacities, the adsorption air conditioning system is expected to be more cost effective than the conventional system beyond an expected period of 7 years, with an expected lifetime of 15 to 20 years.
Resorption systems (RES) utilize the difference in ammonia equilibrium between two distinct salts to produce useful heating/cooling. The salt with comparatively lower ammonia affinity is used as a Low-Temperature Salt (LTS), while the other is used as a High-Temperature Salt (HTS), in a two-reactor system. In this work, BaCl2, MgCl2, NaBr, NH4Cl and SrCl2 are paired with 18 different HTSs, and each pair is studied and thermodynamically mapped for high/low operating temperatures, pressures, COP and energy output. NH4Cl and NaBr are found to be promising LTSs, while SrBr2 and MnSO4 are found to be more suited as HTSs. The resulting four combinations can be used for residential heating in the United Kingdom. The thermodynamic cycle evaluations suggest that the COP range lies between 1.10 and 1.50. In addition, more than 4140 J gNH3−1 of heat energy can be delivered using these pairs for residential heating at 50 °C.